Installing two GNU/Linux
 

I am having a system with limited hard disk space. I want to install both Fedora and Ubuntu. What is the best way of doing that. Can I use the /home,/temp,swap,/mnt,/boot common to both distros. Please Help!.

You can share swap for sure. The rest of them does not take much space. So, there is not much advantage sharing them (except /home). One thing that I can suggest is that you delete /usr/share/docs from fedora. I have not used ubuntu much. But I guess apt has a method of pruning unwanted files. Sharing /boot will be a bit difficult. But you can do that post install if you wish. (I guess you will have problems when you run update if you share /boot)

If you want to share a these, you will have to dedicate a separate partition for each. (It is possible to do it when you have folders, but then you may have to tweak startup scripts)