Psychiatrists are usually pretty good at directing meetings in a way that is most helpful to the patient. I'd try not to worry, your last psychiatrist may have been a dick but there are good ones too so hopefully this one will be helpful to you. Basically he'll ask you what's going on with you, how long for, how severely, a bit about your past leading up to your current state. He might ask about your family life, any drug taking, anything you find helpful, anything that makes things worse, he will probably ask what you want to do about things - medication/therapy.
You might find it useful to write some notes beforehand to get the most out of your appointment, just bullet points would be helpful so you don't forget to mention something you consider important.
Good luck!