Problem

[ToY SoLDiER (DayZ) 31]

How do you open a door? I've died so many times cause nothing works :/

[shao 0]

I guess you have tried doors that can't be opened. A lot of the houses in Arma2 are basically just mock ups.

Try looking for houses where you can look through the windows. Those have doors you can open.

[Dancingg 27]

When you look the door your crosshair should become a symbol similar to this, |><| Or something like that. All you have to do at that point is click the middle mouse, Just make sure you're out of the way of doors because they can break your legs. Also you can scroll on the door and select it manually from the scroll list. Remember not all doors can be opened.

[Fraggle (DayZ) 15720]

If you find a door (one that can be opened) roll your mouse wheel to bring up the "open" option. You can use the mouse wheel like this for many different options.

[Whattteva 32]

Really, those barracks doors are the most dangerous things in the game, man. Barracks is so cramped and the damn door is actually pretty large, large enough to sweep the hallway and anything else in its path (namely, you).

[Dingus (DayZ) 429]

shao is right. As frustrating as this sounds, not all buildings are able to be entered. Since Day Z is using a map from a military simulator (and engine and everything), not all buildings were designed to be. Enterable buildings can usually be picked out by being able to see into the windows, or just remembering what they look like over time.