I've been flashing a few roms lately, and I seem to be running low on internal SD storage. When I look at my file system, there is a lot of junk in there that I don't recognize. Some of it is obviously from apps that were in use on a previous ROM, but some of it I am not sure what it is. I really just want to be able to flash roms or restore some recovery backups (I'm using OUDhs CWM 220.127.116.11, so it is keeping the recovery files at /sdcard/clockworkmod/backup/). Everything else, I am happy to nuke from orbit. So, what dirs do I minimally need? What steps do I have to follow to do this? What is the difference between "factory reset" vs "cache partition" vs "dalvik cache"?