You won't like my answer, but I'm old school.
All new clients are treated equally, like royalty. Over time you discover some are easy to work with and treat the relationship as a two-way street. It's a win win when both sides get what they need and enjoy working together.
Then you have the other end of the spectrum with clients that don't have a clue but expect the world. It's hard to make money from these clients as they monopolize your time and often order the wrong product. They take offense if you try to educate them to keep from making the same mistake twice. Although these types are few and far between, I run them off.
As Ryan noted above it really comes down to risk. Most people don't understand risk and how it affects the bottom line. For example, my employees often get exicted when they quote a large order because the profits could be large too, but it makes me nervous. If a small order goes bad it won't ruin your company. But when we quote a large order I go over it with a fine tooth comb because the risk is great.
A simple method for looking at a client is the "boredom factor". My ideal customer is mind numbingly boring. They order the same product on a regular basis and every order is just a repeat of what came before. Do it again, over and over. Pure gold.