I just have to say: I agree with those who say that it is a matter of getting to know your materials. Some easy tests in the beginning (like the one Aron suggested for example - just pick one and go) and then keeping track of what you are doing and you'll be on your way to good, consistent results, provided you stick to the same material over a period of time. All too often I hear of people disparaging a film after running two rolls and then looking at the negatives.