I don't think it's necessary to count calories, but keep a rough idea of a what a portion size is in your head. The Precision diet mentioned above seems sort of similar to eating Paleo or Primal, though maybe not as strict. I've eaten primally and while I absolutely loved it and had a huge amount of energy, it was just too expensive if you tried to experiment with replacing grains. It was just easier to not even worry about eating any sort of grains.
A really good website about eating primally is www.marksdailyapple.com
I actually found out about this type of diet/lifestyle from someone on here. It's definitely interesting.