Hello!
Welcome to Daxx's first quickie-tutorial called Anatomy of Uke.
Today I will be showing you what parts of Uke that you would choose to target.

On a scale of 1 to 5 (5 being that you need the most force to dismember) this chart shows where you might want to consider hiting uke 1st

Thanks to derbomber for getting a better quality of the image
Aim at the bodypart (with your judgement) that you think will dismember. This will be determined by how much momentum you have built up. You can get momentum by swinging your arm, kicking, etc.
I hoped this helped you alot!