If you live in a state which has allowed the use of marijuana for medical purposes with a doctor's authorization the main thing that you want to do is educate yourself about what the law allows and what the role of the doctor is in your care. Are they required to diagnose you with something? Are they required to sign a piece of paper? Are they required to refer you to somebody? How frequently are they required to see you?
Some of that homework, unfortunately, would need to be done on your behest, because a lot of doctors aren't too familiar with these programs. They're new. They weren't trained in them. Frankly, a lot of them don't have a lot of education on the uses of marijuana for medical purposes. So, that's the main thing is to talk to your doctor in an educated fashion.
In some cases you can actually bring the forms with you that they need to sign by printing them out. For example, in some states those forms are available and you can print them and bring them to your doctor, or at least a photocopy of them so the doctor has an idea of what paperwork would be needed.
Essentially it's a joint decision, a discussion about why you find this useful. Maybe you've tried it before, and you could report those things to the doctor. You could develop in concert a treatment plan.
A lot of times doctors want to try other medications before they try marijuana which is really about training bias, because they are more used to treatment with other standard treatments and they think marijuana might be a last resort. In some cases it really should be used earlier. There are doctors who are now publishing kind of flow sheets, a decision tree, for how to educate a doctor about when marijuana is appropriate. You could find some of those on the Internet.
The main thing in talking to the doctor is educating yourself and developing a plan in concert.