I can attest that this technique from 37signals works really well:
A great way to figure out the weak spots in your product is to demo it live in front of an audience (not just a couple people at an office). Talk through it and read the UI out loud as you click around and do stuff. You’ll notice all sorts of little things that can be improved.
If you pay attention to yourself while explaining to someone how to order a bottle of wine from your site (either starting at the home page, or perhaps as the result of searching), you'll see places where "Why do I have to do that?" or "Why isn't this clearer?" are obvious questions.
On your Web site, it shouldn't take more than 3 clicks for someone to put a bottle (or a case) of wine in their shopping cart, starting from the home page. First click: select "Buy Wine". Second click: choose the wine you want to buy. Alter quantity if necessary. Third click: add to cart. And a properly-designed list of wines for sale can eliminate the third click.
How many clicks does it take on your site? Why is that better? Please leave a comment.