This whole experience has taught me is that there is no limit to what kids can achieve when they are motivated to do so. A set of flash cards are what motivated our son in the beginning. Find what motivates your child and then work on it. You will be surprised at how fast they master the task. Set the bar high and they will rise up to meet it and exceed it. Recently we have started working on the sight words he will need for school and reading short sentences. It is slow going be he is making progress.
But there is nothing like a little proof to bring the story home. Here is a video of our son reading just before he turned 4.