You can encourage blog readers to subscribe to the FeedBurner feed by providing auto discovery mechanism and also by providing a linked Feed icon.

But even after modifying auto feed discovery to point to FeedBurner feed, sometimes visitors will still be using the default Wordpress feed. This happens when they directly type in the Feed URL or when the feed reader uses the default Wordpress feed URL.

Now this is something which you want to discourage. There are mainly two reasons. First, you want to see the actual subscriber count. Secondly, you may want to leverage FeedBurner monetization.

What you need is a Wordpress plugin which will redirect default Wordpress feed traffic to FeedBurner feed. FeedBurner plugin written by Steve Smith (Ordered List) is the best one I think.

Installation is as simple as copying the plugin and then configuring your FeedBurner feed URL. You can also customize your comment feed URL.