Something I would tell my younger self starting to count calories:
1. Dont be too anal about the measurements, unless you are measuring food with high fat content like peanut butter and oil
2. Live a little. Not wanting to eat that one doughnut or meet your friends for drinks every once in awhile just because you've "over-consumed" for the day is not why we choose this lifestyle.
3. Once you've done it enough, you can easily eyeball and guess-timate and identify good and bad choices from the nutrition label.
4. Drinking enough water is more important than hitting your protein goals for the day. Drink water.