Hip: Measure your baby over the diaper at the widest part
Inseam: Measure from the crotch to the ankle for pants, or for how long you want shorts to be. There are two ways to measure an inseam
Diapering inseam: Measure from the crotch of the diaper to the desired length.
In this picture you can see that his shorts would be 2.5-3", and his pants would be 9.5" for a good fit.
actual inseam: In the picture here I am measuring from his actual crotch. I like to do this for my own longies because it ends up giving extra length in the leg for growing room.
Rise: Measure from the belly button, down through the crotch, and up to where the belly button would be on the back.