To my surprise, what I learned over the years is that getting paid for something is mostly based on "the honor system". Sure, there are a lot of terrible people out there, who want to cheat you, and want to steal things, but the vast majority of people are happy to pay for something that is good value. And if you're wondering how to treat these people, look no further than how you yourself would like to be treated in a business transaction.
My business model was the repair shop that worked on my car. They were my first clients (I designed a car parts catalog for them), and my first mentors. From them I learned this -
• Provide a good product or service. Seems simple enough, but you have to know your business before you can start charging for it. For me, it meant getting my degree in Graphic Design at ASU, and more than that, learning to be really good at what I did.
• Learn how to do estimates and proposals. This is very, very difficult and is the main reason why so many Graphic Designers fail. You wouldn't drop your car off if the shop had no idea what it was going to cost to fix it, so why would someone hire you if you don't know what you plan on charging them? And just giving them an hourly rate is no good, either. You have to take your hourly rate, calculate the time it will take to do the job, and then tell them. You have to do this as quickly as possible, and you have to stand by your estimate. If you can't do that, you are out of business. I took classes at Phoenix College to help learn how to do this.
• Submit the final bill with pride. If you've done the job, and done it well, you should have no hesitation to submit the bill. Again, if you can't do this, you are out of business. This goes back to the "honor system" I mentioned before. The vast majority of people are glad to pay the bill if you have been up front with them and you have provided what they need.