Here's my advice, based on how I play crawl.
runequester wrote:1: When a weapon is listed as, for example, +0 / +1, what does this reflect exactly? I was assuming its attack bonus / damage bonus, but can anyone clarify? I had a hard time finding this in the wiki.
First number is accuracy, second is damage. When you get two numbers listed like this, accuracy is always the first number. You can remember this by noting that accuracy / damage is in alphabetical order. As for the exact effects they have, it's fairly self explanatory, but damage is generally regarded as being the more valuable of the two. Note that +5 damage really means "up to +5 damage" - it's random.
2: Skill training. What's the general consensus on how many skills to train at one time? On one hand, I get worried about advancing too slowly because I train everything at once, but I also get worried about missing out on important skills in case I find a good weapon later on.
When you're learning the game you can probably get away with "automatic" skill training. When you're better and know what the various skills do, it's often a good idea to train one at a time - whatever is most valuable at the moment (for instance, if you want to get a certain spell castable, you should train the skills that will get you that spell). Don't worry about this too much though, you can win the game without micro managing skills.
One rule I go by is that I try to only train skills that will be useful to me right now. I will never train a skill that *might* be useful in the future. Planning too much in advance tends to make you less versatile, and you can wind up with a gimped character (eg, you train fire magic and conjurations high, but never find any high level fire spells). So, don't worry about what you might find later - focus on the stuff your character has now and train your skills according to that. If you find a cool weapon later or a powerful spell you want, then you can adapt - switch to training other skills. This is easier said than done, especially when you're still learning the game.
3: For characters that have "dodge" based skills, like the gladiator or monks, how much should you try to stick to light armours ? I was having a bit of a hard time judging where the balance is between better evasion and better armour class. Ditto for spell casters I suppose.
The choice between light and heavy armour depends on a few factors. One is aptitudes - some races are much better at dodging skill than armour skill, so it's better to train that. Another is spells - casting is easier in lighter armours (or robes, which have no penalty). There's also stealth - you can't be very stealthy if you're walking around in plate armour.
I would say that on almost every character, you want both your AC and EV to be good. Therefore, medium armours (-3 ev penalty or lower) are a good choice for most "hybrid" characters (combination of spellcasting and melee), especially in the lategame when you have access to various dragon armorus (the best armours in the game, usually). For "pure melee" builds you should wear the heaviest armour you can, unless you're a particularly dodging focused race (note, you can cast spells in heavy armour, it just takes more skill). For "pure casters" you might want to stick with a good robe (eg archmagi) because you'll hardly ever be taking any hits.
But still, it's usually good to have both stats at a reasonable level. If you have super high EV and low AC, you'll dodge most attacks but can take huge damage from some. If you have the opposite, you won't take much damage but you'll get hit all the time, and ranged attacks will be a pain in the ass.