1996 Pontiac Sunfire not holding a charge?

[Roll Tide!]

the battery in my sunfire will not hold a charge. i have replaced the alternator, the starter, and the fusible link. I have checked the ground wires for each item, and everything seems to be fine. All the battery terminals are in good shape? how am i supposed to find out if one of the wires is shorted out? and how would a wire just automatically short itself? this jus happened all of a sudden. also i have checked the fuses and they seem to be fine? is there ANYTHING else i need to check out?
battery was tested as well. it was good