You didn't really say, but I presume you mean you do tie your shoelaces, but they come undone all the time?
If so, let me share with you the secret of shoelace tying: http://www.ted.com/talks/terry_moore_ho ... shoes.html (it's only a 3 minute video, well worth watching). Most NTs don't know this, either, by the way, so if you learn it you will probably be top shoelace-tier at your work place.
Here's the knot I normally use and recommend - the "Ian Knot": http://www.fieggen.com/shoelace/ianknot.htm
You end up with the same knot as what's shown in the TED video, it's just a faster way to do it and the explanation is in text and diagrams, which is quite helpful. For comparison, here's the same guy's explanation of the "granny knot", which is the one most people know: http://www.fieggen.com/shoelace/slipping.htm
Now, when I really, really need the knot to be secure (in a situation where tripping over can be fatal) I use the "Double Slip Knot": http://www.fieggen.com/shoelace/secureknot.htm I don't bother with this one normally, because it is a bit trickier to tie and I don't think I've ever had the "Ian Knot" come undone. This knot also helps with long shoelaces, though - it "uses up" a lot of the length. Or you can just do the standard knot twice.
Oh, and a little suggestion to the OP: edit the topic title to mention tying shoelaces, so people can get some idea of what the topic is about. I'm sure there are others that can benefit from this, too.