You can use a keycap puller or bent paperclip to pull the keycap off and get a better look. If it is broken, or the spring is missing, replacement parts can often be found at clickykeyboards.com and some parts can be obtained through pckeyboards.com (Unicomp).
So as to prevent things from getting broken, or getting broken further, I like to remove the small keycaps around any large keycaps first so that I have more maneuvering room, and can better see what needs to be done to remove the larger keycap.
You can search the forums for images of keycap pullers, both of the commercial and homemade variety.