If you want to get a good jam session recorded, a good thnig to do .. if your friend has a laptop or a video camera... is put different mics into different computers/laptops then set them next the different amps... or set the camera next to an amp (preferably not the bass amp because the bass frequencies could shut the camera off; it could do that anyway, but it's more likely, the closer it is). Then, you can mix all the different elements together by ripping them all to a main computer. That way, you're jamming but you can still lower some instruments, add some eq to 'em... uh, stuff that's probably a bit too complex for now, so maybe just put a mic on a light fixture in the middle of the room and you should be good for now!

When you get to actually making songs, I'd buy a smallifier and hook it the back of your cables and plug it into the mic port of your computer and record each instrument individually.

Because of poor listening skills. :D