You dont want to reset your check engine light, cause that means you have a problem... hence the 'check engine' light comes on. First start off by checking out your manual. It says that you should make sure that your gas cap is tightened to 3 clicks.

Have you dont any sort of work on your car lately? Installing an intake? lights? indiglos?

Last time I looked at my Accord's tach, the rpms idled around 800-900, and started around 1200-1300 when cold, until warmed down. I dont understand the fluxuating question. Is it a 5spd or auto?