Accurate framing and parallax correction



Any tips on how to very accurately frame ? I am getting more on film than I see in the finder.

I used the 28mm for a large group shot in landscape orientation and noticed that the right hand side has more room than the left hand side.

For the 45mm in portrait orientation, I saw some stuff on the left (the top from the perspective of the camera) on prints that didn't appear in the finder.

Yes I know the finder is only 90% and the prints may cover more than that, but is it even on 4 sides ? Any quirks in the parallax correction I need to be aware of ?