Take it slow like Cheryl said. Just cause he is in his 20's doesn't mean he is to old to act like a 2 year old. Start off in the round pen saddle him and let him move around and see what he does. If he allows you to get up in the saddle and just sit there do that and keep progressing from there. But give him more credit than you think, he will know if you are nervous about something and may try to take advantage. I had a 30 year old and still have a 28 year old, let me tell you they are smart and been around the block. We lay off our horses here in the summer since it is so hot, so little to no riding for about 3 months or so. If some one they didn't know went to get and ride them they would act a little goofy. But if I or my hubby went out to get them they new we weren't fooled. There are times that they act like they forgot everything they know but after about 5-10 minutes they know it is to much effort to put up to much of a fight and just go back to being there old selfs.

Good luck, He has a lot of years left.