When you boot the live dvd, it has the gparted program on it. I use that to create the partitions I want before I install. The reason I do it that way is because I create the / partition (8 GB), then /home (450 GB) then a /test partition for trying out different os's (8 GB), and then my /swap (2 GB).
Then when you install, choose the "Something Else" option, and designate the existing partitions, / and /home, that you want to use.
You can actually create a /home after you install, but it is certainly not recommended. I wouldn't try it.
How to Create a Separate Home Partition After Installing Ubuntuhttp://www.howtogeek.com/116742/how-to-create-a-separate-home-partition-after-installing-ubuntu/