The tag or flag usually goes on the tip of the antenna and the numbers at the base of it. Unless you're in an area where a lot of RC boats or cars are used, I wouldn't worry about using them. I never did with the cars I had or the boats I had. Surface transmitters use totally different sets of frequencies than aircraft transmitters so don't worry about them.

Our club has a board where you have to put your club membership card up or your AMA card up on the clip that corresponds to your frequency. No clothspins at all. Most everyone there is 2.4 now anyway.

I scared some guys when they saw my float plane up in the air at the lake right next to our field. I told as many guys as I could that I was headed over there and that I was on 2.4, but some people either showed up after I left or didn't remember.