Just went through this (as you've probably gathered from the blizzard of posts about Kali) and we started looking for a yard when we very first got serious about viewing horses. I knew we could have done DIY in terms of horse knowledge and ability (our share mares were on a DIY yard) but because of my work schedule felt I needed either full or assisted. There were some restrictions to all of the yards we looked at . . . no vices, only geldings, no outdoor school, no hacking, etc. . . . but at least we knew what our yard options were as we went to see horses. It wasn't deliberate, but we only looked at geldings (so the "no mares" thing wasn't an issue anyway). By the time we looked at Kali, I had knew which yard I preferred AND knew the yard we really liked had space.
It IS a daunting process. Never mind trying strange horses in front of their owners (not to mention wondering if said horse is going to kill you or your teenage daughter) . . . there's also choosing a livery yard, choosing someone to do the vetting (if the horse isn't local), choosing a vet, choosing a farrier, choosing a saddler, choosing an equine dentist . . . yada yada yada.
The thing to remember is that decisions can be un-made. If you don't like the yard you're on, you can change. Ditto farrier, vet, trainer, dentist, etc. Experience will show you that you either made the right decision or that you'd rather be somewhere else.
I found our yard advertised in Horse and Hound . . . local tack shops generally have yards advertised on their noticeboard. Riding instructors are a good source of info too.
You're right . . . it is a puzzle.
N