If walking through a crowd, try to keep your gun side bladed away from folks as much as possible. (I'm talking mostly about holster/belt carry, of course.) Perhaps even keep the arm or hand on that side between the crowd and your firearm. Naturally there's only so much of this possible, but it's a good habit to get into.
Try not to bend over in such a way that your hip-carried gun prints against your jacket, etc. Bending at the knees is generally healthier too, so why not? Also good to remember to focus on the folks around you as much as that nickel you dropped,

I won't go into much about dealing with "homeless" folks and the like, except to say not to be so focused on one person you forget they could be part of a team! For example, I don't mind telling even the smelliest wino what time it is (like he cares!) but I won't drop my eyes down to the wrist watch, the watch comes up near eye level. And anytime a fits-the-profile stranger approaches as if to start a conversation, I'll risk their ire by taking a look around at my 6:00 from both sides. Sometimes they know what that's all about and get highly offended, but so what?
Now, some of you might say that one needn't be CCWing to do this stuff, but for me it's kind of like the chicken and egg analogy; Which came first: Did carrying make me more situationally aware, or has becoming more aware increased my willingness/desire to carry? I'd suspect the answer is..some of both.
Alright, chime in with yer own small, subtle stuff learned from the world of pistol packin'. And/or nitpick my take on the topic..