I started on my 20th birthday. A buddy of mine took me to a pool room where we played a little. Soon after I started going with my friends to play every friday, and it became the highlight of my week.
There was a house pro at the room we frequented who I used to enjoy watching. He was a long haired hippie type guy who generally showed up stoned to some degree, but he could play a fine game regardless. Even though he offered lessons, he always gave my buddy and I free pointers which I always followed religously.
After almost a year my friends lost interest in playing pool every week, but I was still very much engrossed in it. So I started practicing during the day before I met up with them to go to the bar.
As it is, I still love to play and I honestly couldn't care less if there is anyone to play when I go to the pool room. I'm always happy to play myself, it's meditative in a way. For a few hours the most pressing concern on your mind is "How do I get on the 5 ball"?