Great ideas, Dave!
I've had up years and down years with numbers over my career, but more up than down recently and there's only one real reason why: The focus of the culture is on developing good young men, having fun, and winning along the way....in that order. Still have days/weeks/moments when I lose sight of why I do this and think my only purpose is to build a team that wins championship, and that's definitely part of what I want to do, but ensuring they're having fun has to be goal #1. Even with this in mind, in a decade of coaching, I've still never had a team that didn't have at least 2-3 kids quit, sometimes there's nothing you can do, the sport just isn't for everyone.
Here's a few things I've found works:
1) Make Dual Meets fun! If the student body gets fired up about going to a wrestling dual, more athletes will want to be a part of the program. A major disadvantage we have is that we aren't a "glory" sport, but shining a light on the hard work the boys do helps with recruitment and more importantly, with retention. Look at what Brownsburg has done in their turnaround there. Turned the sport into an event that is must-see. You think it's a coincidence they have stud football players showing up in the room winning state titles?
2) Monthly, in season or out, we try to do something as a team that is fun. Go to Cedar Point. Take the team to the Indiana Dunes. Go camping. Team Camaraderie goes a long way when interested kids ask current wrestlers why they wrestle. If they respond, "It sucks, but I love it," you may have an issue recruiting new kids. When they say, "I wrestle because it's fun," something has gone right.
3) Involve yourself in the feeder programs. We have 4 Middle Schools, 2 feed 98% of their students to us at HSE, the other 2 are split between us and Fishers,It'd be easy to ignore the other 2 schools as 80% of their kids go to Fishers HS, but I try to run a practice or 2 at each MS immediately following the HS season. And I make it fun! I try to get to know the MS Athlete when they're in 7th grade, so when I reach out as they are incoming, they already know me. This was a lot easier at Mooresville with 1 MS, but I have a great involved staff of Assistants that help out and attend MS events and practices as well so that they're always seeing someone with HSE wrestling gear on in their corner.
4) Spend time, as a head coach, with your JV kids. Not just on the mat, but off the mat too. A lot of coaches have a tendency to focus on the best wrestlers (State Qualifiers and Placers make us look good), but I've been around to see what happens to a program when the emphasis is only on the Varsity kids winning as much as possible and the JV kids get run off. What happens when those Varsity kids graduate? You wind up with a lot more holes in the line-up than you should have because average wrestlers or developmental kids who may have turned into a solid starter leave because they didn't feel anyone cared about their success. I attend every JV event that doesn't conflict with a Varsity one. I may be late due to practice or Youth Club, but I show up to show the kids that I care, and I have 3-4 Assistant Coaches that understand why working with these less capable wrestlers is important and do a great job in practice and at meets. In my experience, these are some of the most valuable people to surround your kids with.
I'm going start stealing some of the ideas Dave uses as well.
Ultimately, you have to find what works for each school. All 3 that I've worked at have been different, but ultimately, the #1 reason kids do a sport is to have fun. Sometimes, it's hard to remember that, but if you do, growth isn't far behind.