It's alright to not tip. If you're at a restaurant and a waiter is serving you, then you are not the only person they're serving for the day. When you pay the bill and give them no tip, they will simply remember you as "that jerk from this morning", but soon enough you will be forgotten among all the other jerks that don't tip him throughout the day. Besides, some restaurants have started doing a 10% service charge, like an automatic tip.

It's only good to tip if you've particularly enjoyed the meal.

Also, drink Mountain Dew while you're there.