This is a good opportunity to plug Ian's Shoelace Site. I used to have some winter boots that had slippery laces and they would come undone all the time. But Ian has a Secure Knot which only takes a bit of extra time to learn, but is so secure AND comes undone easily by simply pulling on both loose ends at the same time. Pulling on only one loose end doesn't unravel the knot. I feel like it should be mandatory for runners to learn this knot.