In the March 2011 issue of INC magazine, Jason Fried of 37Signals wrote an article about How to Make Money. He notes that everything takes practice. How do you make money? Selling. And that takes practice.
Some notable quotes from the article:
"People's reasons for buying things often don't match up with the company's reason for selling them."
"When you describe things in terms people don't understand, they tend not to trust you as much. Trust is important [in sales]."
"Sell only things you'd want to buy for yourself."
"People are happy to pay for things that work well."
Basic lesson: want to make money? Sell stuff people want to buy.