Cork tunnel

When rinsing out a wine bottle, use a thumb if you're going to shake water inside the container, as opposed to the cork (especially the plastic-rubber variety); the hole left by the corkscrew can act like a small tunnel through which the agitated water can travel, which could in turn coat you with a wine-water mixture.

Mosh pit attire

If you are attending a concert and you want to be on the floor in front of the stage, be careful what you wear- the crowd could surge and knock off a hat or glasses, and then you might never see those items again (especially true if wearing glasses).

Single CD purchase

If your friend asks gives you money to buy a CD that you also want, check to see if the album contained in shrink-wrap when you go to purchase. If it's not, you can just buy one CD, rip it at your computer, and then give your friend the genuine article, saving yourself the money of having to buy it yourself.

Two nice things that don't work together

Use metal-based inks on glossy paper. Anything else will smear.