First time ever on a bike for me was with a girlfriend riding a DT125R, I quite enjoyed it! After that I also was with a childhood friend on a CBR600 doing silly speeds on not politically correct places, I was a teenager back then.
Now, I would get on the back of a bike for a short ride home or something like that, I wouldn't really enjoy it though, but wouldn't be afraid either.
I really enjoyed touring with my girlfriend, although touring BMWs are quite better at carrying passengers than most other bikes.