Well dual-booting Vista and W7 will be a LOT easier than XP/Vista or XP/W7, because Vista and W7 use the same boot manager technology.
It should be a simple matter of :
1) Create your partitions structure
2) Install W7 either by a) Booting from DVD or b) Installing W7 from within your Vista setup, ie open Vista, pop in the DVD, run setup.
Method 2a) would result in both Vista and W7 considering their own system drive as C: with other drives relettered accordingly ; method 2b) would preserve the drive letters used by Vista in the W7 environment.
3) Use VistaBootPRO if desired, to rename, reorder, & change entries in the resulting boot menu.
I can't think of anything else essential that would at all need to be included if W7 is installed after Vista
I guess there is one line of possible issues if someone tries to install Vista _after_ W7, ie if the 100MB hidden boot drive has been created on his/her system ...