its literally the easiest thing in the world.  go into your next door dispensary and ask them to recommend a doctor.  they will be more then happy to. call the doctor ahead of time to see what you need to bring. chances are nothing. if you dont actually have anything wrong with you lie and say you broke your wrist a few years ago skiing and now it hurts every time the weather changes. or back problems, or trouble eating. anything really. protip: insomnia isn't a good one.
depending on how strict your dispensary is they may let you shop that day, most likely, and if they follow the rules, you'll have to wait a couple weeks until your card comes in the mail.
when it does come shop around, find out which shop has the best product for you. if your signed for 6 plants, whichever dispensary you finally sign with will be able to grow 6 more plants, in your name, in exchange they hook you up with better prices.
hope that was helpful.