You can enter as many times as you like but you must leave a different tip each time you comment.

FORBES: Connect

Why would I leave a big tip on clearly lackluster service?

FORBES: Transparency Is The Key To Leadership

Leave a big tip if appropriate.

FORBES: Finding Your Heroic Inspiration

We rather get reminded of this when we foreigners forget to leave them a tip (I have actually had a waiter in NYC tell me, as I was sitting down, that he had to tell me as a foreigner that a 20% tip was normal).

FORBES: Greg Mankiw's Excellent Question: Why a $9 Minimum Wage? Why Not $90? Or 90 cents?

Revenue Ruling 2012-18 clarifies that the IRS believes a tip to be what you and I would leave our server in addition to the bill.

FORBES: Pastor Who Refused To Pay Applebee's Service Charge Becomes Unwitting Poster Child For Server Pay And Tax Issues