I recently learned that the reason I’ve had trouble all my life with keeping my shoelaces tied is that I was taught to do it incorrectly. There are two major steps to tying a standard shoelace bow, and each step can be done in two mirror-image manners. If you pair the steps incorrectly, you wind up with a slip knot, and that’s what I’ve been doing.
You can tell visually whether this is happening because a correct bow is horizontal (across the width of the shoe), but a slip knot will tend to orient itself in the direction along the length of the shoe.
The fix is to do one or the other major step in the opposite manner. For instance, if you start by passing the left lace over the right one, instead pass it under.
I’ve tried explaining this to various people and met a lot of skepticisim. I just did a Google search hoping that someone had documented it, and sure enough, found Slipping Shoelace Knots by Ian W. Fieggen. In addition to the well-illustrated explanation of the slip knot problem, he also presents several other improved shoelace bows, including his own “Ian Knot”.