Spoiler
To open doors you don't have a key for, you have to 'k'ick them down. However, many doors are trapped, and kicking the doors will set off the traps, which can damage you and destroy your equipment. If you want to kick down a door safely, the best thing to do is to get to full health, drop all your items at least a few squares away, and then 'k'ick the door down from a diagonal angle (ie. 7, 9, 1 or 3) which will keep you from getting too much damage and will keep your items safe. The detect traps skill helps you know ahead of time whether a door is trapped or not, and you can buy the detect traps skill from Yergius in the bandit village, but there are certain conditions you need to meet before he'll teach you that skill.

Spoiler
The best way to not get stuck wearing cursed items is to not put on items in the first place unless you can be reasonably sure they aren't cursed. One way you can be reasonably sure an item isn't cursed is to see how much a shopkeeper will pay you for the item. If he offers a high price, it's probably safe. If he offers a low price, it probably isn't. Dropping your items on an altar tells you whether your items are cursed, uncursed, or blessed, but the altar has to match your alignment. If you're chaotic use a black altar, if you're neutral use a gray altar, and if you're lawful use a white altar. The manual explains alignment more thoroughly. To remove cursed items, you can uncurse them with scrolls of uncursing, bless them by dipping them in holy waters, or destroy them with traps, scrolls of item destruction, or very angry gods.

Spoiler
if you kick a door and it says that 'it does not budge at all' it means that the door is trapped, doors that say 'it does not budge' are not trapped

Spoiler
if you've equipped a cursed weapon and want to get rid of it, you can find a ratling fencer and wait for him to disarm you, or attack a grey ooze/jelly untill the weapon is corroded untill it is destroyed, acid traps can destroy you helmet (Ctrl and the T button) but beware that you dont kill yourself doing this, and remove your other equipment. and a blessed scroll of uncursing uncurses everything in your inventoey.

Spoiler
if you get hit in the face by a glob of hot mud, the blindness will never go away unless you wipe your 'F'ace