How do you count calories?

I mean it sounds like a pain in the @^&, but I really need to lose ten pounds...I'm about 5'7'ft and 165 lbs. How many calories should I be eating a day if I'd like to steadily start taking off the weight? I have no idea how many calories I eat a day now, but I'd like to start keeping track. But what would be the easiest way to start doing this?