Well with websited its easy as you make sure you stay in control with logins and kill scripts until paid. Logo design i usually request 50% deposit from a client and then when i present draft i try do it in person. However if i have to email its watermarkd and a low quality..... Despite all this what happened to me once was somebody received the draft design and then proceeded to try recreate the design so they would not have to pay the balance of the deposit.
These people tend to have businesses so what we do as a graphic design community is we hit up the business facebook , website all over social media bassically naming and shaming the business. The buety of it is , whilst this could get you in trouble for slander , i dont do it my friends do the naming and shaming, and if one of them gets a bad deal i help out. When the person in question asks me to stop i just say i am doing nothing , what my friends do is not in my hands.
He ended up paying after a month of trying to ban facebook accounts.
I think the cost in reputation to his business was ten times my deposit lol.
JUst reffering to some of the above thoughts, when i started as a graphic designer. A decent price shows you have confidence in the quality of your work. Yeah you may be full of it maybe ? but a low price is going to show you dont value your skills, land you crappy customers looking for a cheap deal.
As a business owner however would you like somebody to do your advertising whom is confident in what he does ? or somebody who is looking to take any job for any price ?