Depends what size they are,  195/75 x 14  air should be round 32 or 34
205/65 x 15 air should be set to 34 or 35  by the time you have driven 10
miles, your tyres will warm up to their proper working temperture. If their
16 inch tyres 34 front and 35 rear wont hurt at all. Keeping the proper air
pressure is up to you. The more times you check, the less tyre wear will
occur, also if you havent had a wheel alignment for awhile, it may pay to
have one to see if ya wlignment on the front end is normal, on some cars
after 2002 front and rear alignment is needed.

Hope this helps

Peter