While the above linked blog post was written mainly to an audience of women--who are probably mostly already aware of this technique--I thought it might be a useful item to share with the guys here on The Nylon Gene, especially if you're new to wearing hosiery. You may not have the slightest idea what to do if/when this happens to you.
If you're wearing ACTIVSKIN legwear with shorts--despite how durable we try to make it--some time you'll look down and see a 'run' (Europeans call them 'ladders') starting to go up or down your leg. Just do what's described in the linked article and you can (hopefully) stop it from becoming too noticeable. Just don't waste any time getting to it. A lot of times, once runs start they can get worse pretty quickly. It doesn't hurt to have some clear nailpolish handy somewhere.
Oh yeah... and if your hose look like the photo above, better just give up on 'em.