I've been tying my shoes wrong for my entire life! Just a few days of tying them correctly and they haven't come untied yet, a personal record! Actually they normally don't come untied, but that's because I end up having to tie a double-knot. This explanation makes it very clear how to tie a single knot (a reef knot) that will only get tighter as it sits on your shoe, not looser. The video from the site is here below, but check out the actual explanation if it's knot quite clear.