Be sure and check in using nwa.com check-in so that you will have printed boarding passes (with seat assignments) in your hand when you arrive at the airport.
This will also speed up your time at the ticket counter (if you have luggage to check) or if you are using a rollerbag and not checking anything, just walk to the checkpoint and continue on to the nwa gate.
You really only need to be at the airport 35 minutes before departure if you are not checking luggage and have used nwa.com checkin.
Good luck!
RC