Looking back, we did it all kind of backwards. Son did about 200 generic emails to coaches within a specific geographic area. If one responded with a camp invite, I'd research it. If it seemed like one son would be interested in, he would follow up with an email. If the conversation seemed good or for some reason we really like it, he went to a camp. We ALWAYS combined that with an academic visit.
On the downside of this approach, he went to camps at eight schools across the Midwest, and ended up at a school two hours from home where he went to his first camp.
On he upside, he said every camp and visit showed him more about what he wanted, or didn't want, in a school.