I want to expeiment with my friend. pointers please?

It's good that your trying to experiment. If I was you I would stay up way late make sure your parents are fast asleep then start the conversation off with girls then to female celebrities then male celebrities and from there see what happens. Don't directly ask him unless his reactions says "let's do this". If he says hes gay or bi then go for it. If he says he curious hopefully he's nothing like one of my friends who told me that and then forced me the rest of the way out and said that he's not actually curious that's just "the mean part about me". My point is understand the risks and benefits of this. You should be okay since you said he's not homophobic. Also you should try to get all his views on sexuality be prepared for a negative response and have lots of evidence to back you up. example: you don't necessarily control the part of you brain that controls your boners. and if an odd awkward silence comes up ask if he wants to look at some porn. Good luck