cek, if you are considering starting your own group, just make it known on the message boards. It is good to try to get a group that is small, especially starting out. Maybe 3-5 people. It is easier to coordinate a hunt with just a few. Get acquainted with these people before the hunt. Maybe you could arrange to meet in a public place, like a coffee shop or something, and get to know them. This helps you to avoid any unpleasant surprises about your companions on the night of the hunt.
At first, try to stick with people 18 or older, if possible, because a younger person can really cause you some headaches if they happen to get hurt while out there with you. Just a little bit of a precaution. Later, after the group is more established, you might be able to take people under 18, but you should require their parents consent in writing, with an emergency phone number for reaching a parent or guardian, in case of an emergency. Since you are 18, they can hold you legally responsible if anything happens, if you have no proof of parent's permission to let them join you.
Hope this is helpful. =) Let us know how you are doing. We will be interested to know about your group and the hunts you go on. Good luck in finding some companions!
Mare