Boy Scout Troop 604
Ideally, Scout patrols will be made up from their real patrols. In practice, it rarely works out that way. We either have too few Scouts (and therefore only 1 or 2 from any given patrol) or have large imbalances (i.e. 2 Scouts from one patrol and 6 from another).
A good patrol size for a camping trip is 4-8 and for a backpacking trip is 3-4. For backpacking, smaller is better due to size of pans and quantity of stove limitations.
We usually let the Scouts organize themselves into patrols and just make sure they aren't too imbalanced.
How To Plan a Camping or Backpacking Trip