I have an ASUS U56E. It's an i5, 8GB RAM and 750GB HD. It came with Windows 7 installed. Using a partition manager (gparted) I shrunk the Windows partition to 190GB since I rarely use the OS but since I paid for it I kept it in case I need it... The recovery partition says it's 27GB.
Okay. So what I like to do is have separate partitions for each Linux OS and a separate data partition designated for /home. At this time, I usually find 16GB to be adequate for my Linux installs. This may vary depending on what and how many applications you install. I will tell you, I'm no lightweight and my current Mint 15 install says my root partition is at 39% capacity.
Here's what it looks like
On my data partition, I have a /home/ray partition where I have my Documents, Pictures, Music, Video as well as .thunderbird directories. Anything that can be shared between the distros... BUT I created a separate "Home" directory for each distro install. For Ubuntu 12.04 my "Home" is /home/ray-precise, for Mint it is /home/raymint and so on. I could have made my Mint login "raymint" and "Home" folder would be created automatically upon first time logging in but instead what I do is during install I specify my normal login name but before logging in to the GUI for the first time, I login on a VT (Ctl-Alt-2) and edit the /etc/passwd file, where user info is stored. I find my login entry and change the name of the "Home" directory to the one I want. Now when I login to the GUI the folder name I want will be created. After logging in, I delete Documents, Pictures, Music, Video folders and create symbolic links to the folders in the /home/ray directory (ex. ln -s /home/ray/Documents /home/raymint).
By doing the above, no matter what distro I boot, my data is all there. The only caution I'll add is if you use Ubuntu One to sync your data it will not work with folders that are symbolic links.
So for this setup you have to install properly and I have to tell you from memory so my description will be brief. The installation program will get to a point where it asks if you want to install side by side or replace current OS's. You want to choose "Something Else". You will manually create or edit partitions. When setting up mount options for the /home directory make sure you don't change the filesystem type from what it is or format it, or you will lose your data.
I may revise this entry to give better instruction, in the meantime feel free to ask me questions.
