You might be able to find out about a rendezvous through your local shooting club/ range. You can also probably find out more information by looking on the web for muzzleloading activities. I have seen listings for events for several states. That should give you someplace to start.
As far as clothing etc. goes, I just wear blue jeans a shirt and a baseball cap. I do enjoy the other shooters who put time and effort into their period clothing. But for me, that just isn't in the cards right now. Mostly I go for the fun of it all. :thumbsup:
I have heard of shoots where they are strict about clothing and such, but I have never gone to participate or observe. Most of all, remember to enjoy yourself.