If you receive poor service, don’t just suffer in silence.  There are other alternatives besides leaving a small or nonexistent tip.

If your requests are not being responded to properly. ask to see the manager.

A good manager will want to be aware of problems so that he can fix them.  It  might be enough to save your dining experience.  After all, that's a far bigger expense than the tip.

If it's awkward or you feel uncomfortable asking for the manager while still at your table, do it as you leave.  You will have limited his chance to help during dinner, but he will still want to know about the problem.  Sometimes you may be compensated for the problem, although the dining experience will still be ruined.

If you think the waiter doesn't deserve a tip, don’t leave one.   You may still want to leave a partial tip for your busboy, when you speak with the manager.  If others were helpful, don't punish them.  This will make it clear that you do tip for good service and that your waiter didn't provide it.

Tell him that you appreciated his exceptional service.  Most people take pride in their work and will appreciate your compliment.

Ask to see the manager as you leave.  Just as with poor service, the manager wants to know about excellent service.  Most managers will recognize their stronger employees and encourage good customer service.

Tip accordingly.  If your waiter has gone above and beyond normal expectations, you will want to leave more than the standard 15% to 20% tip.  Providing you with a wonderful dining experience deserves more than the usual compensation. 

If you will be returning, find out the waiter’s name.  Next time you can request  him and look forward to another great dining experience.

Good service usually brings a customary 15% to 20% of the total bill before any discounts or coupons.  Always tip on the original amount before the discounts or coupons are applied.  

If the service was excellent, you should leave a larger than standard tip.  Something over 20% is appropriate.  The exact amount is up to you.

In some cases a restaurant will automatically add a tip, usually 15% to 18% of the check.  Normally this applies to large parties.  More restaurants seem to be including tips to all bills as a standard policy.  Always check your check to see if an additional amount is warranted.