If you enter a shop, you will be expected to look around, barter and buy stuff. You can leave without buying or selling anything, but remember that at times shops might contain important or powerful items.
To buy something in a shop, you have to pick it up first. The shopkeeper then will block the exit (there seem to be so many thieves around nowadays) and wait for you to pay (which is done by using the p command). If you do not have enough money, you probably will have to leave the item(s) behind.
You can also sell items in a shop to raise more funds. Not every shop will buy everything as most of them are rather specialized (e.g. on potions or scrolls). If you want to sell something, just drop that item. The shopkeeper will immediately tell you how much he is willing to pay and then you can decide whether or not to accept the offer.
ADOM supports two types of wishes. You can wish for abstract things and concepts like friends, money, wealth, strength, health, and other things.
You can also wish for items. Such wishes can be very useful, since ADOM features many powerful and rare items. If you do not want to wait for a certain item, just wish for it as soon as you receive a free wish. Since wishes are powerful but not very precise magic, you can only wish for very general items. For example, it's not possible to wish for 6 blessed long swords (+6, 1d8+6), but you would rather have to wish for long swords or mithril plate mails. If your wish is not formulated precisely you might get something other than what you are expecting -- so be careful!
To restore a saved game, just start ADOM and type r on the option screen. If you choose that option a tiny menu will display the available games to be restored (if there are any). Please note that this menu only displays a maximum of 20 saved games (without telling you that there might be additional saved games). This should be sufficient for most purposes. Depending on your screen resolution even less games might be shown (e.g. 16 under DOS).