[tapostrophemo]

These work great for keeping your pants cuff out of the chainrings:

http://www.amazon.com/Pant-Cuff-Clips-Bike-Bicycle/dp/B000MM...

[Groxx]

My family has always just used two strips of velcro. Mate ~1/2 of a few inches each, and the remaining tails stick to each other. Wrap & go.

Advantage: you can wrap it around the handlebars / a part of the bike when not in use, so you never have to remember to carry it.