If you're nervous about meeting someone, sometimes meeting at a public place (eg a metro station if arriving on public transportation) and walking together to your hotel / home helps break the ice with regular conversation.
Have towels / bottled water on hand as some bodybuilders can perspire when posing & flexing.
Also, if you want a soft / relaxing session, then some slow music on in the background really helps with the mood.
To be honest, I'm sure if you respect his limits and show the normal social courtesies of any host, you'll be fine.