One of the best ways is to note great CM's before you leave the park at guest services. Remember their names, locations, times, what was so good.
In lieu of that, use guest communications email to share the same information.
http://allears.net/pl/contact.htm
Absolutely the best thing to do Dan!!! I've stopped at GS several times. The really funny thing is that when I get up to the counter, and the CM asks what they can do for me, and I tell them I want to make a CM report, they always get white, and their mood subtly changes...I watch for it. They pull out the complaint card and ask me what the issue was. When I tell them that I'm not there for a complaint, but a compliment, the visual relief is almost funny. They always tell me how nice it is to have a guest say something wonderful about the CMs!!!
So, yes, stop off at GS. That compliment card will be noted in the CM's file, as well as go to their manager. I remember one time my friend and I rode ToT, just as the park closed...late!!! The CM there, who puts you on the elevator, was exceptional. I do a lot of theater, as does my dd. I tell her all the time that even though she's done a show 8 times, she needs to keep it fresh because there is someone in that audience that has never seen the show, and they deserve the best experience possible. So, when this young lady behaved as if we were the first run of the day? Incredible! She was great...actually one of the bests ToT CMs I've seen. So to be that great, at park closing, was really impressive. We stopped, as we exited, and asked to speak to a manager. He promptly came over, with, again, a look of concern. We told him about this CM, giving her name (which we both checked out!!). He was so appreciative, and thanked us profusely.
So, please, give that compliment to someone in authority. Sure, it's nice to hand out compliment cards to the CM at the time, but to have something officially noted in their file? Hugely beneficial.