I usually wear sport briefs, usually like this style:
http://www.getitcovered.ie/image/cache/ ... 75x675.jpgAside from finding them comfortable and sexy, somehow I have more WD's whenever I sleep in them. The feeling of being firmly 'packaged' kind of turns me on to begin with, which probably helps with causing erotic dreams.
I should note that I usually try to buy ones that are more elastic, rather than 100% cotton. Cotton by itself doesn't stretch much, but briefs with a little bit of elasticity tend to let my erections get fuller, which I think encourages my WD's. Usually I look on the packaging, if it says something like 50% cotton and 50% polyester, it's usually a good pair.
Sometimes I do get in the mood for boxer briefs. Having my thighs partly covered with snug fabric can be a turn-on too, though I prefer the briefs if I'm seeing my girlfriend anytime soon.
