Door latches come in many varieties---from strong latches that secure front doors to small latches designed to keep store rooms or closets closed. Opening or unlocking your door latch involves examining the design to see how it works.
Look for a metal button on the latch mechanism. Try sliding the button up or down to release the lock. This design is more common on latches attached to front doors or other important entranceways.
Look for a keyhole anywhere on the latch. If the latch has a keyhole the only way to unlock it is with the correct key. If you have misplaced the key you should call a locksmith to open the door.
Look for a switch mechanism on the latch. Try sliding it left, right or up and down to disable the lock.
Try lifting or sliding the latch. If there is no lock you should be able to quickly open the latch. If there is a handle near the latch try pushing it down. This will raise the latch on the other side of the door, if present.