Updated April 2012.
Lens manufactures do everything they can to prevent photographs from getting lens flare but if it's used correctly, lens flare can really create a feel of romanticism and mystery in an image.
When it comes to kit, any lens will work but it's easier to get flare with less expensive lenses. You can use a tripod but if the sun's not in the right position you'll have to lay on the ground so working hand-held will be your best option.
Techniques to try
As you're trying to create something a camera has been made to prevent, it will do everything in its power to do just that. So you need to work in manual, trust your histogram and rely on your own ideas and judgement. You need to ignore your camera when it says your subject is blown out and don't be afraid of an overexposed background as this will help you get the look you're trying to create.
Just before the sun goes down is the best time to try this technique but if you can't get out at this time you can lay on the ground to get the light behind your subject. Do remember to adjust your exposure so your subject doesn't come out as a silhouette. Don't be afraid to use overexposed backgrounds as this will add to the effect and switch to manual focus if your lens keeps searching.
Don't think you have to always be outside either, this technique works just as well indoors with your subject against a window or patio doors.
Flare can also help you disguise a less than ideal location and turn what would be an ugly image into something more exciting. Don't think your subject has to be completely visible either. Hiding some of their face behind the burst of light can create the mysticism you're looking for.