Within limits, it would be desirable for you to observe a professional
framing crew operate a framing nailer, both roof framing (1-3 nails at
a burst) or subfloor attachment (more nails driven consecutively).

Observe how they use framing hammers on the job as well. Typically
20-23 ounce heads, straight claw and 16" handles.

One caution - since the nail is driven in a single stroke, be aware of
the angle of the nailer to the surface. Either hold it square to the
surface (avoids having the point blow out the side of the second piece
of wood) or move over so that the nail point still ends up completely
enclosed in the second piece of wood (as in toenailing).