FAT32 can be read by both OSs. I run dual boot on my spare machine but
xubuntu on main hard disk and win on the second - i save all files to
a FAT32 partition on main HD. I don't know if that's the best way...
just what i did as it's easier to install. I think it probably depends
how big the HDs are - on this machine i'm just using two older drives,
win on a 10g and xubuntu on 40g. The only thing i use windows for is a
CAD app and a scanner that doesn't run on linux.