How to avoid a diluted drug test?

Did a urine drug test recently and it came back diluted. I had one cup of coffee and one glass of water about two hours before, then took the test. I am not concerned about anything coming up positive as I don’t take any drugs, but I definitely want to avoid another dilute as I assumed the amount of liquid I consumed was normal. Am I supposed to not drink anything before the test? Do I need to eat before? How do I make sure it doesn’t come back diluted again?