Ken is right about how oblivious people are. Unless your print is captain obvious, or your gun goes skittering across the floor, 99.9% will never notice you are carrying a handgun.
Also, unless you've completely lost concealment... NEVER touch the gun through your shirt or whatever. That's pretty much a sure fire way to tell everyone else that
something is there. If you pretend its not there everyone else won't know it's there, either.
When I started carrying one of the guns I used to carry was a Sig P226. I carried it outside of the waistband, in a Don Hume JIT slide (basically a belt slide holster that just covers the trigger guard and the middle of the gun and nothing else) with a spare mag in a carrier on the other side. The only thing I had concealing it was a shirt. It even printed a little, but nobody ever noticed it.
I've even had cases where my gun made that loud THUNK noise as it bangs into the wood in a restaurant booth/wall/etc.... but still, nobody ever notices.
-Mike