Haha, I'm no help--- I didn't make any real friends my age in my 4-H groups, I gravitated to the adults. Maybe you would have an easier time talking with the parents in the group? Usually, they're not so loud and hyperactive as the kids in the group, and often more helpful. People love to talk about themselves, so ask some questions and give easy feedback. "How long have you been riding? When did you start 4-H? What's your favorite thing to do here?" Etc. Etc.
Put a little thought into how the other person feels about what they are talking about and that oughta start forging the relationships :)