You can also, if you have them partitioned separately, share
filesystems. I used to do that back in the day, with Slackware 2.x and
RH 3.0.3. It's just a matter of mounting the appropriate filesystem to
the mount point.
You could probably still do the same with if you are using lvm, as long
as you don't get a namespace collision, e.g. both systems don't use
vg00 for the volume group name.
That said, as an earlier poster said, if you have the resources, use a virtual machine.
On my debian machine, I need to install redhat on one of its partitions and so make it dual boot . Can you please let me know how this can be accomplished?