I would also agree with TG. Speaking in generalities, as everyone will look at things their own way, playing with others can work out as a good way to explore yourself, types of things that you like, or don't like, so long as all parties understand that you're NOT in a committed, monogamous relationship. Play is play, after all, and while there should be certain levels of negotiation and after care involved, I still don't think it measures up to the commitment sex brings to a traditional couple.
As a young dom who is just beginning (Okay, just recently allowed!) to find his true interests, I think that taking the time to learn different techniques through playing with others is one way for us on both sides of the fence to better prepare ourselves for when we do meet that One who does take our mind, body, and soul.
The most important thing is honesty. While TG seems to have taken a harder, straightforward approach, not that there's anything wrong with that, I might also recommend something along the lines of "I'm new to this, and since I still don't know specifically what I like most, I want to let you know that you're not the only one I've chosen to explore with." There's a little bit of psychology behind the difference in phrasing... You won't be giving them the impression that you need other people because they're inadequate, and you're also letting them feel special by reminding them that you chose them to begin with. And if they don't understand, then, well, you'll know what to do from there.
Best wishes on your journey.

- Mark