On your first booking, you may find that you get a little over excited and cum early. If you can get hard again in an hour then go for it. If you think you'll struggle to get hard again in an hour then 30 minutes might be all you need on your first booking. It's natural to be nervous, so try not to worry too much. An experienced SP will have experienced this situation many times before so can help you with your nerves and guide you through the process. As long as you are respectful then you should have fun. On my first time the SP told me to try to relax and enjoy it and go with the flow. The SP will probably suggest things like licking their pussy, kissing, how to get them naked, blowjobs and sex positions.
I hope you have fun.