For me a church must be first and foremost doctrinally correct in the essential core beliefs.
Just for clarification, does this mean you seek a church that believes what you believe?
How do you make that determination?
I am tempted to make a smart-alec statement like--"'doctrinally correct' and 'what I believe' are one in the same!!!!". Though in a less joking voice, I do believe what I believe is doctrinally correct; after all why believe it if i didn't think it was right. (But that discussion could lead into another thread).
How do I make that determination? First I tend to look at the material the church offers; usually they have the church's core beliefs laid out somewhere. (I can also find this on websites.) If I know what college the Pastor attended; that usually helps. Getting a copy of the church's constitiion or charter can help too. Second, I may talk with people, like staff. And then there is listening to sermons, live or taped helps too. But I do this step mostly to know if this is a a guy I can listen to. Not every speaker fits every listener.
I also tend to do this in steps. There are certain beliefs that are essential. (Again that could be a whole thread alone) and then there are doctrines and practices that I consider very important and would want, but I could be flexible there; and then there are some that are some doctrines and practices that aren't as important; some I might not even have come to a firm decision on myself. (I wouldn't say, not important, just not as important as the first two catagories.)