I always get a 50% deposit. My contracts almost always require complete payment upon completion of the installation. Sometimes, I will let them pay the balance in 12 monthly payments. My contracts say "In the event that the Buyer fails to make the agreed upon payments, the Seller reserves the right to remove the sign installation."
Every once in awhile, I still get burned, like I did on 10/02/2008 by a jerk named Chris Yoo who owns an Econo Lodge motel and was desperate for a sign. For some reason he can't understand that there are city zoning laws that govern the size, number, and placement of signs. In his zone, he is only allowed one sign on his building. Two days before we did the installation, he was demanding that we put the sign up that day. He wouldn't understand that the sign was still being manufactured. Then he demanded that we raise the parapet sign up, so that the letters would stick up above the roof line. We told him that that was illegal, and if we did that, the city inspector would red-tag it. Roof signs are outlawed, and no part of any sign can extend even one inch above a roof line, and they are very strict about this. When my technicians were installing the sign, he came out and told them to raise the sign up above the roof line. They told him again, that it just wasn't possible.
Now he refuses to pay because we wouldn't install a second, shipped in sign on his building without a permit (over $1,000 fine if you get caught). He needs to go to city hall and bitch at them about the sign restrictions. Refusing to pay me makes him a low-life rip-off dead beat. I know he owns other motels around the country, so think twice before working for this jerk. He is one of those problem customers that intends to not pay contractors by making up lame excuses and objections about the work done.
There is nothing illegal about having a black list of bad customers. http://www.angieslist.com/Angieslist/ is a black-list of bad contractors. Any customer can put you on that list if they want. Also, there are many websites like Travelocity, or Price Line dot com that let people give negative reviews of motels and restaurants, and that is essentially a black list.
Watch out for Chris Yoo, owner of Pacific Motel Development Corporation.