On the maps, the bottom left corner is A1, letters going up the side of the map A to P maximum and numbers along the bottom 1 to 16 maximum. Unless stated otherwise, all areas are 16 by 16. Occasional single letters have been used to refer to specific locations on the maps.
Some encounters are fixed, others random. Once you have the skill Read Tracks, cast this on first entry and mark each purple square as an X on your map. Do the same with True Seeing which will show staircases, doors, teleports and other important items as yellow blocks. Mark as a ?.
Some Xs may turn out to be NPCs but it's well worth knowing where the tough fights are likely to be. Random fights aren't usually so hard. Occasionally I couldn't work out what a ? referred to; nothing seemed to happen, or there'd be a message saying something like 'the room is bare' so these are still on the maps as a ?.
Some monsters carry excellent treasure the first time you find them. These are not always replenished when you go back a second time but it's worth a try! Quest items, as far as I can see, are always replaced should you need a replacement for some reason or another.
Equip yourself with the best lockpick you can find. Only a low level one can be bought, others are gained from fights. I found the best was a blue and kept this in the slot between my character's feet for ease of use.
I have tended to say 'use a blue lockpick' in the solution and on the maps. But I haven't always noted which doors need a lockpick and I gather a blue one isn't actually needed until the Thieves' Den, Level 5.