I do both DB and KB snatches, and I always start with thw weaker hand, but that's just me.
There are quite a few common set/rep around, e.g.:
1) The weaker hand as many reps as possible until failure (or close to it), then switch hands;
2) Few reps (e.g.3-5) on one hand then switch hand, back and forward until failure (or close to it)
3) Change hand every rep.
It totally depends on what you are training for.
Hope it helps,