Also, seeing when the trims go lean or rich can be a big help in diagnosing.
If you get rich/negative trims at idle, and lean/positive trims during cruise or accel, you look at the MAF sensor first.
Lean trims at idle that trend towards normal under accel or cruise.....vac leak.
Rich idle trim, trending towards normal under load.....stuck fuel regulator.
Normal idle trim, trending lean under load.....fuel pressure problem (low pressure).
Just generalities, but it sure is a good starting point figuring out drivability concerns.