I've known my friend since middle school, but we never hung out outside of class. He recently confessed to me that he was autistic. I knew he was something because he always had an aide with him, but I never asked. He graduated high school with me so I'm not sure how extreme his autism is. He invited me to a movie night and I couldn't go because of a camping trip, then he invited me to go camping and I said I would go.

He seems upset lately because of some things he wrote on a facebook status, and then he got angry with me because I started suggesting things we could do when we go camping and told me "I'm planning the trip, so I get to decide what we do". I've never hung out with someone who is autistic and I would like to know some general rules about what I should and shouldn't say around him because I don't want to make him upset. I know I should let him make all the decisions because he got upset about "telling him what to do" earlier. It also seems like he is going to try to pay for everything which can be expensive. Should I let him pay or offer to help pay, or would that upset him? Should I pack extra stuff for the trip in case he forgets? What else should I know?

Thanks.