Better check those cards and letters before heading to the mailbox today. The cost of a first-class stamp went up one penny Sunday from 33 to 34 cents. Postal Service spokesman Rich Watkins wants everyone to be aware of the change.Watkins says putting a 33-cent stamp on a letter could lead to trouble as most businesses don’t accept mail without proper postage.He says there’s been little talk of the rate increase, but a lot of action indicating people are aware of it.Watkins says there are a variety of 34-cent stamps available.Watkins believes it’ll be a few years now before the price of a stamp is raised again, but he says there’s no guarantee with fuel and heating prices continuing to go up. Watkins says the extra penny for postage will cost the average household 15 cents a month.