No doubt,quality and price is the most important factors which you should consider.
1.Quality consistence—-How to control the quality? With this question, you’d better visit the workshop (especially SMT workshop) that you may choose them as your factory. Because whether the SMT workshop is small or large, the production could be produce, but the different is the quality consistence. Anti-static, moisture-proof and dust-proof is the three basic rules in the SMT workshop(It’s also most important). And the workshop should record operations with ISO9000. I have went to some workshop, the window is open!!! And you even shouldn’t wear shoe’s cover, hat and ESD wrist strap!!! They are big risks which would cause the problems in quality. Even though the production looks ok as leaving factory. But the failure rate would be increase after user use it in several mouths.
2.Price—-The price making is base on the component choosing and the cost of processing. So how to choose the best component with low prices is the crux of the matter. Although PCB assembly already contain component sourcing, you’d better communicate with your manufacturer positively about component sourcing. It not just save your money， but also make sure your production quality too.
3.Cooperate with manufacturer directly. As someone said “the most important thing is to make sure they have the processes in place that you need.” You should kown, many factory don’t have the processed you need but they still want get this business. So they take over your business then outsource it to someone else. It may bring many troubles you would’t want meet.