Here are some suggestions for surviving the early game.
Play as all classes until you're familiar with all of them. Later in the game you'll have the option to change classes, and it helps to know what you're getting into. Low-STR classes(e.g.: Alchemist and Sage) are not as much of a liability as they might seem, since they can gain as much as +3 STR from green-powder urns.
Plan to map out the village and forest completely. The game's difficulty spikes up quite rapidly once you leave the forest, and the village and forest are the easiest way to find nice items. The nine areas of the forest can conveniently be explored in an S-shape ending at the dungeon entrance without significant backtracking. Later in the game you may not be able to afford the time to explore every nook and cranny, but you won't need to if you are adequately prepared from the early game.
If there is a 1 space gap between you and a monster, do not move towards them, since that gives them the first attack for free. Instead, stand still or move in a lateral direction, let them come to you, then attack.
Don't be afraid to use items, if you're in a tricky situation. Saving them for later won't help if you're dead.
Put on every armor piece you find, unless you're already wearing something better on the specific bodypart (compare AC as you change armor, the less, the better). Hexes on armor are not particularly dangerous, and a single dispel hex will de-hex everything you're wearing. Also, a -1 iron shield is better than no shield at all.
Avoid using unidentified scrolls/potions/rings until you are able to bless a scroll of identification, which will identify all that you carry (up to 51 items) at once.
Wands are important. Spend your initial $1000 on a wand of fire or ice. It usually has 5-6 charges. You can sell it for $500 after spending those charges, in order to regain enough money for another wand. (Don't identify it beforehand, as the number of known remaining charges will likely net only $100-200.) If you are a blacksmith, use ice on most monsters to save fire wands for smelting, or simply make use of black mushrooms on hand and try to gain Fire Vision through a scroll of knowledge as soon as you can.
Return to the village a few times while exploring the forest to sell unused loot and buy more stuff. Money weighs you down, and you can usually save weight by spending it on items. By the time you reach the dungeon, you'll want a grappling hook, at least one scroll of blessing and one of identification, and a wand or two. Rings of agility are good temporary investments too. AC is your most important stat for long-term growth. Save potions of strength for when a green powder urn gets you past 18.99 STR (Strength has no maximum value).
If you stumble across the ocarina, sell it for $2500 and buy more stuff. It's only useful much later(or not at all if you manage to become five-dimensional early enough) after you find a scroll of enchantment, and even at that point the enchanted ocarina can practically steal itself out of the shop.
Don't bother fighting dregs, anssks, stun jellies, weird fumes, retchweeds. They're slow and will usually give a nasty effect when you melee them. If you're a woodsman or have a disposable ranged weapon (like a crossbow or boomerang), feel free to toss things at them. They are not important enough to be worth spending wand charges. Eating one anssk is beneficial but not urgent. Weird fumes are fun to play with, but you don't really need 16 fingers and the confusion effect can be annoying and potentially lethal in the wrong situation.
- Slywerts will clone themselves, killing the original kills the rest as well. Try adjusting your position to hit several with a single wand blast. Clones are difficult to melee, and wasted swings spawn more clones.
- Berserkers just hit hard.
- Secitts will clone themselves, and every clone will also have the ability to clone themselves. Extremely irritating. If you can't kill them fast enough, and more than 3 are around, stop wanding, leave the level and explore elsewhere. Even though their HP and damage are low, after awhile they will clone so much that you'll waste all your time killing more secitts.
- Corpses can give you a rotting disease, forcing the consumption of your blessed curing. They don't have a lot of HP but it's good to not let them have the opportunity to melee you.
- Serpents move 50% faster than other monsters and reduce your STR.
- Ghosts (from the deaths of other characters) can cause fear, causing you to lose control of your character for quite some time. They also are difficult to hit due to their AC.
Characters that are poorly geared may also wish to use wands on the following: bear, homunculus, hrygar. Homunculi have low HP but have a stun attack that can be very dangerous if your first attack misses.
When your pack fills up, leave some non-essential items in a pile right before exiting a map cell(preferably next to a trader). Orcs/Gnomes/etc can only pick up items if they are on the same map as you, so the items are relatively safe when you leave the map.
Bless a scroll of identification after your pack fills up and try to bulk-identify unknown items. If you found an unexpected windfall of loot, you might need to do this twice. If you lack the needed scrolls, they are often available in the village shop.
Later, when you have a lot of items, remember that a scroll of blessing while confused will bless each item in your pack with an independent 60% probability. This is extremely important for sages but useful to all classes. To confuse yourself, a potion of mead is the safest way, but a weird fume or ull might work in a pinch. You can read two blessings in one spurt of confusion to boost the odds to 84%.
You won't find all of these, but any that you DO find can be potentially game-changing, so it's good to know what windfalls to look out for.
- potion of phasing - lets you steal from shops! Wait 1 turn after drinking in case the potion is cursed.
- scroll of knowledge - super useful to get more skills but don't consume this until level 9, otherwise you'll get a skill you were booked for anyway.
- scroll of transport - allows access to the bazaar, where you can buy almost anything. (I'm so jealous)
- ocarina - sell this for cash unless you have a scroll of enchantment, in which case you have the second-best escape mechanism in the game (the first being dimension travel)
- red bag - amazing for item management, you can take your stashes (or at least some of them) with you. Consider extincting sandiffs and archmages, as their attacks have a small chance to blow up your bag.
- ring of regeneration - Gain 1 HP per turn. Really useful for surviving in dangerous places with poor AC. Note these stack if you have multiple.
- ring of protection - passive trap detection. Absolutely critical if you intend to explore the dungeon safely.
- wand of displacement - mundane, but critical. It's always valuable to be able to teleport yourself away from a dangerous situation, and even better if you also have a ring of locus mastery.
- wand of polymorph - you can aim this at yourself if you're the high-risk-high-reward type. More conservative players may want to wield a wand of restoration while playing around, because super-weak creatures like retchweeds will drop everything except their wielded item and be unable to pick them up.
- wand of tunneling - remember these can also be aimed up and down. It's not a common use, but you might want to consider taking an early visit to Vidur's Temple to grab the guaranteed amulet of infravision and Lazlul's Rope to get back to the first floor.
- wand of wishing - incredibly rare and powerful. Take a break to think about what you want to wish for (or consider anything else on this list).
After the Forest
Yay, you survived the forest! Now what?
You're probably about level 6-8 at this point. Your first priority should be getting to level 10 by whatever means necessary. That awards your class completion skill and opens up a lot of options
If you stumbled across a portal to Slaeter's Sea, that's a viable option. Ocean creatures give pretty good experience, and ranged weapons are quite valuable to exploit creatures that are exclusively aquatic or exclusively terrestrial. Don't go to Gioll unless you have a very large amount of ranged weaponry. Exploring River Vid is plausible, but risky. There are some difficult creatures out there. Having a ring of regeneration will help because there are a lot of somewhat safe places to hide, depending on the threat.
The Dungeon is the default choice if nothing else presents itself. If you lack a ring of protection, then trap doors can be pretty devastating, since 20 meters is considerably more difficult than 10 meters. Hopefully your kit of identified gadgetry from the forest can hold you through until level 10. Use whatever you need to survive.
At level 9 you will get your valuable class capstone skill. Your next action will vary depending on your class:
- Alchemist - Return to your item stash and determine which potions you can create with your known recipes. Second life and dimension travel are critically important. Then cash in whatever utility skills you can. If you have empty vial(s) or a few scrolls of wonder, consider taking a trip to Azare's Plane for other potions. With terraforming and dimension travel, you may want to try hunting for random artifacts.
- Blacksmith - Return to your item stash and melt available metal items. If you have a black mushroom, that can be used to save on fire wand charges. Make yourself a runesword and a mithril mail.
- Conjurer - Relocation is good but is essentially a one-trick pony. Your next course of action will depend more on your existing item collection than your class skills.
- Sage - Return to your item stash and rewrite all your crappy scrolls into blessing. Do a confused-blessing to bless 60% of your items. Thus you essentially gain 1.6 AC from each scroll. Throw all these blessings on an armor piece that you don't expect to replace (bracers, greaves, gorget). With the extra defense you can focus on grinding in safety before proceeding to dangerous locations.
- Viking - The weaponmaster skill improves your damage and attack speed, which is great, but there's nothing special to do at level 9. Continue killing things. Your next course of action will depend more on your existing item collection since you have no active skill.
- Woodsman - Taming sucks. Terraforming is good for artifact hunting, but don't overdo it since it has a chance to animate the surrounding terrain. The level 5 skill, Fletching, is the best. Bring a lot of ammo and try farming River Vid, sniping at land creatures from the sea and vice versa.
This ends the early game, but some ideas of where to proceed from here follow --
Faleryns are a reasonable choice for farming XP. They reproduce like secitts and are worth a good amount of XP. If your AC is good enough to take minimal damage from them (say -30 or so, maybe -20 with regen) you can allow them to take over a zone you are done with, and slaughter them by the hundred. This can greatly speed up the acquisition of a second class's skill. If you can't find a faleryn, you can make one by polymorphing a tree. River Gioll is a possible place to farm them since the area is pretty easy to get to, and not needed for anything else. If you have terraforming, you can drop a tree in the dungeon, polymorph that, and farm them in a room with an easy choke point.
Rangers are also a good choice for farming XP, they multiply when attacked in melee, and they also drop items. Unfortunately they have a stun attack, so you need to be extremely careful to not get stunlocked by them. So the AC requirement is more taxing (-40 to -50). You can summon a hostile ranger by using a scroll of extinction on something else. Slaeter's Sea is a good place to do so because you can confine them to one island without completely overrunning a zone with rangers.
Even better, if you have psionic power or enough AC, find a level with a draugr. Keep killing it and letting the body revive itself. This should net you an excellent level boost.
There are four random artifacts in the game: in Wasteland, Slaeter's Sea, Crypt, and Chaos. Although you can't guarantee that a specific desired artifact is in the game, most of them are the best you can equip in their slot. The alchemist is best suited to finding them, but others can greatly profit from seeking them out.
Below is an extract from the manual. It details early game advice by none other than Tom Boyd and Rob Vawter, the game makers themselves:
"The experts disagree on the most beneficial order of class selection:
Rob's favorite method is to start off as an alchemist. He consumes all of his unknown potions and then drinks his blessed potion of curing if his physical health has been adversely affected. He steals everything from the trader if he stumbles across a potion of phasing. By starting as an alchemist he learns to create a potion of second life before any other class.
Rob then changes into a sage if he has not yet learned writing. He remains a sage until he does so. If he is positive that the scroll of transport has not yet been created, he sometimes remains a sage until he learns to write it at the 31st level of the sage class.
Rob then suggests that you become a viking and remain in this class. The extra attacks which are gained at 5th level of the viking class become necessary against the powerful creatures beyond Midgard.
Tom disagrees with Rob:
His favorite method is to start as a sage. This provides a stylus at the start rather than having to find one after becoming a sage later. He then becomes an alchemist next on. As soon as the skill of alchemy is learned, he switches to conjurer to learn all spells. Then switch back to being a sage again. Sages learn how to write a scroll of transport at the 31st sage level. If he has already found a scroll of transport, he will skip the second sage training phase and switch to the viking class for the rest of the game to gain the extra viking attacks.
Tom usually skips the woodsman and blacksmith entirely, but occasionally will start as a woodsman. He enjoys slaughtering everything with the crossbow."