Don't share home between different distros. Put your home on the same partition as the system, and have your last partition for data. You can then create symlinks for Documents and so on.
There are different ways to set up multiboot. You need to have Grub in mbr, and then you can either boot all distros from the same Grub, or you can install Grub on the partitions for the systems and then use chainloading. I for myself prefer to have a separate partition for Grub, not connected to any of the installed distros, and manually add entries to it.
Ubuntu, Mint and Crunchbang all have Grub2, and they usually find each other and Windows. One way which is easy to begin with, is to just let them install Grub in mbr. That means the last installed distro will have control over Grub, and if you remove that distro, you need to reinstall Grub before you can boot.
you can read about Grub.
I'm too tired to go deeper with this now, but this should get you starting. You can change later if you want another way to boot your systems.