I just let it rage on, ain't nobody gotta be lookin' there anyway. Just cuz I'm aroused, don't mean I'm trying to cause offense or force anyone to get down and dirty with me.
To hide it, just shove it in a pant leg.
EDIT: In a clothing-optional situation, just cover it with a towel, lay on your stomach, or dive into a pool/hot tub.
To get rid of it without a mess, just squeeze it discretely. Or, of course, think unsexy thoughts.
In a clothing-optional situation, you can't really get rid of an erection discretely.
I suppose you could jerk it through your pocket if you don't mind the mess, and the fact that you could spend a long time working on it. (Of course, clothing-optional situations would leave you in the open.)
This is more relevant in Indiana than it is in other areas, because it is actually illegal for an otherwise-clothed man to have a visible erection in public.
I try to trap it so its flat with my panty waist holding it flat to my stomach not that it would happen often.
I just pull down my t-shirt to hide it and let it go away on its own.
Besides what has been mentioned there is always the time honored tradition that if you have something in your hand use it to hold in front of you.....if it's possible to do so. In the office I constantly have some folder or something in my hand, and I have used them if needed.....and yes they have been needed at times.
The other thing to make them go away...in the similar vein as Dudealicious, I think of my ex-mother-in-law.