Tying shoelaces is a tricky skill for little kids with little fingers to learn, but it's an essential milestone too. A great trick for teaching a child how to do it is to use a skipping rope first.
The Montessori for Learning blog writes about difficulty trying to show a young child how to tie her shoes because it was hard for her to see all the movements. An article on eHow offered the skipping rope solution (and a rhyme that goes with it: "Build a teepee, come inside. Close it tight so we can hide. Over the mountain and around we go. Here's my arrow and here's my bow!"). The skipping rope gives the kid a larger view of what's happening, and it's easy to practise with.
You could also try showing your child the quick Ian Knot technique.
How to Teach a Child to Tie Shoes With This Nifty Rhyme [eHow] Tying Shoelaces [Monessori for Learning]