Depends where you are located. In my neck of the woods (MN) most of the colleges and many of the top club and HS programs will hold camps in the summer. Any camp you can work alongside seasoned coaches will help you gain experience. I had to learn quick, fast and in a hurry after being shoe-horned into a coaching/spotting job. I learned a ton by watching (I wish we had YouTube back then!!) Watching warm-ups before high-level meets was very helpful. I would watch how they spotted skills, and listen as they coached their kids. I was able to convince a couple of camps to hire me on to help with the lower-level athletes, and from there I could listen, watch, and eventually help spot the bigger skills. Double-spotting is a great way to learn with relatively low risk. Coaching/Spotting clinics are excellent ways to learn as well, but you may have to bring some athletes along.
I second what JBS says about coaching kids and placing them where they belong. That's one of the things I love about coaching where I do. You can just help them advance their skills. More than a few times I've caught static from some club coaches when their athletes have come to our camps, and we've worked on skills that the coaches didn't want them working yet-because "they need to spend more time on beam" or the like. Maybe its my lack of gymnastics background prior to coaching, but I've always failed to see why the fact a kid can't do a handspring on beam means they can't work BHS-full on floor...