I wish to add something to the exellent link provided by jrdavis.
There are two notches, one on each side of the chamber. This is where the extractors go when the bolt is closed. They often get clogged with carbon and grit and can prevent proper extraction. I've heard that toothpicks can be used to clear the notches, but a set of dental picks work real good. Sometimes the grit is packed in there tight.
Also I do not recommend disassembling any further than the pictures in the link. Those little springs and clips quickly disappear and can be a bear to get back into place.
While disassembled, inspect the firing pin. One side should have a slight bevel and the end resemble the blade of a screw driver. If it looks "rolled" or "blunted", it could cause misfires by not striking the rim cleanly. The firing pin should also move freely within its slot. They can bend from being dry fired.
Good Luck.