1. Never Tip for meals less than $20 after taxes.
2. Tip 5% if your appetizer comes before you finish you first drink.
3. Tip 5% if they got your meal right.
4. Tip 5% if you waited less than 3 minutes after you main course to be asked if you would like some coffee, the dessert, or your bill.

These are my standard rules for restaurants for taxi cabs I only tip if the cabbie takes a direct route on a meter.