When you have identified 10-20 agencies that seem to fit your criteria, write to them to get their information packets concerning China adoptions. These will give you information several different ways. First, these will continue your education about the China adoption process. Second, you will see if the agency selects and presents information in a way that communicates clearly to you. Third, you will see if the agency can deal with simple requests in a timely manner.
Few things are more irritating than having to wait weeks for an agency to perform a simple task.
After all of the information is in, look at it carefully and in detail. You will likely find that only some of these agencies seem to be the better ones. These should go on your short list. You should try to pare your list down to a half a dozen or so to go into the next phase of the process. The next task is for you to interview agencies.