Chosing Reps/Sets/Rounds, etc...
 

I was wondering how Crossfit chooses the reps/sets/rounds for their WOD. Does anyone know?

I am trying to make some workouts uo on my own, but want to make sure that I am chosing an appropriate scheme - one that is taxing enough.

Depends on what your goal is....
1-5 build strength
8-12 build hypertrophy
15+ build endurance
Sets going for 30sec-2min are glycolitic
Sets going for 3+min are oxidative
Lactic Acid rounds are around 1-2min for GH release

So you can do:
Small reps with plenty rest for strength
Small-Moderate reps of several compounded movements back to back for more glycolitic/GH training
High reps of bodyweight or low weight for oxidative
Or mix it all up in one workout like a 21-15-9 format

Not hard to do......Just change the focus day to day.

Bleu-
One of the CFJ's covered program design...I think the title was something like "A theoretical Template". it's good, certainly worth a read.