Manage People's Expectations

The single most important skill that I've learned so far working in IT is the ability to manage people's expectations. When providing services for people, make sure that you can deliver at least what you promise. If you're promising to provide a certain quality of work, be sure to meet that quality of work. The people that you provide the service for will be satisfied and perhaps come back to you for more service. That means more money for you. Unless they think you're going to work for free, then do the exact opposite so they don't come back.

Managing expectations takes a little bit of practice to accomplish.

Don't promise things that you can't deliver.
Promising things that you can't deliver will always make you fail in managing people's expectations. If you don't believe me, you can try this simple experiment. Tell your date or significant other that you want to take him/her to a fancy dinner, maybe at Ruth's Chris. Instead of going there, take them to McDonalds or Burger King. See how they react to that. I'm willing to bet that they're not going to be too happy unless they like $1 dollar double cheese burgers with extra pickles more than they like fancy dinners.

Deliver what you promise to deliver on time or earlier.
If you promise something by a given date, make sure you deliver by that date or sooner. Typically when choosing a delivery date, I give myself a little bit extra time to take into account the unforeseen. In addition, if you give yourself an extra day or two as a buffer, if you deliver early, you've more than met their expectations.

I've been using this strategy to deal with people and I've had very good results. I still do have people wanting me to work for free, however, but that is a separate issue.