Of all the focal lengths, I personally think wide-angle lenses might take the most getting used to when it comes to creating compelling imagery that takes advantage of their unique properties and avoids their pitfalls. This helpful video will give you some great tips for taking better shots with them.
Coming to you from Nigel Danson, this helpful video examines the use of wide-angle lenses and how to create better photos with them. Wide-angle lenses are probably my favorite, but there's more to them than simply capturing more of a scene. Personally, I think the most commonly overlooked quirk is that they often require a strong foreground element to make a compelling shot (though not always), lest there's a tendency for the resultant image to look a bit vast and flat. When you find such an element, however, you'll often be rewarded with an image that has a natural, multi-layered composition with pleasing nuance that naturally leads the eye to the grander background elements (if, for example, you use a rock in the foreground of a mountain shot). Once you get used to the way they tend to behave, they're one of the most powerful tools you can have in your bag.