Where the seatbelt anchor bolts are will be the hardest to find. Measure, mark, note, whatever. I find it best to do every thing else first, saving the trim at door sills for last.
All i can add to that is Be careful !
The threaded studs on the bottom of front seat tracks will bite you. They had temporary covers over them in the factory. I have found a few of those under original carpet.
The hooks in the floor for the rear seat bottom bite too.