I waited tables for a lot of years starting in high school and ending well after college. I slung pizza, sushi, sandwiches, Osso Bucco, Veal, $3 mugs of beer and $300 bottles of wine. I did high end and low brow. 3 tables in a night and 30. It turned out to be, in my opinion, as educational as my college degree. In fact, I suspect it might have been even more valuable because I draw on lessons I learned in those kitchens every single day of my career. Here are the top 5.

1) People are there because they want something. It's the same with your business. Everyone is calling you for a reason. It's your job to figure out what that is. You'd think it's easy in a restaurant right? Wrong. Food is just the beginning. Some people are there because they want you to be their tour guide and tell them cool spots in the city, some are there to be waited on hand and foot, some people want to learn about the type of cuisine you're serving. The nature of your relationship with clients will be the same. Some will want complete help, all the time, on call. Some will want to feel like they came up with all the ideas you came up with. You need to know the difference.

2) Learn to make suggestions. This one was big for me and really helped me later in my career. Here's a restaurant secret: most people will order whatever you suggest to them. They want you to take the whole menu and condense it down to your 1 or 2 favorites and they will choose from those. Like a menu, lots of businesses provide too many services and people don't want to choose from all of that. They want you to (from number one) "find out what they want" and suggest something for them. If you are one of those waitresses that can't spot a tired, hungry person that just wants you to tell them what's good, you won't get anywhere.
Learn to do this in business too. Between blogging, video, podcasting, Twitter, and the millions of ways to connect with people online I've found it best to figure out a few that would really work well for them and let them choose among those instead of the whole laundry list.

3) Reading People 101. Part of finding out what your client or even your own boss wants means you'll have to read people quickly. Malcolm Gladwell has a great book called Blink that has some great theories on quickly picking up information about people. People in the service industry are some of the best people readers I've ever seen. Recognizing in 2 seconds that your table is really over-hungry and arriving with a bread basket before you even bring waters can be the difference between a great table and a complete disaster. If food is taking forever and you can see your table becoming frustrated, I'll bring out the best appetizer we've got for free because $10 on the restaurant is nothing compared to a pissed off client. Now that Twitter allows complaints to be national in a moments time, this is even more important.

Learn to read signs of annoyance in your clients or boss and head them off before the explosion.

4) The Sky is the Limit. I was drawn to the restaurant business for 1 simple reason: I could make more money there if I tried than I could getting paid hourly. This set-up always appealed to me (and still does, it's why I have my own company) because I'm the type of person that needs to know that great work will be rewarded. Try this with your employees. Reward great behavior and incentivise them. Entrepreneurial employees are good to have around but they like to know that if they go the extra step, you will as well.

In the service industry, I knew that if I was cranky and did the bare minimum, I wouldn't make much money and on the flip side I could make all sorts of connections and money if I was extroverted and friendly.

5) Taking Care of People. My Service Industry friends and I always talk about this but you'll never see a group of bartenders or restaurant owners squabbling over splitting a bill. Why? Because it's uncomfortable and in an industry that works on tips, uncomfortable is bad. I'm not suggesting you pick up every tab for a client or that this is all about client dinners. The point is, you have to be sensitive to awkwardness at meetings, presentations, etc. and learn to eliminate it.