Ah, the good old fashioned burnout. There aren't many things out there that give you the sensation that a burnout can bring you. That being said, it's important to execute it properly, or things can go south pretty quickly. Not only will you look stupid and possibly get hurt, but you'll mess your bike up, too. So, check out this video, and take notes on the proper way to do a burnout.
The technique is not nearly as hard as you might think. The most challenging part will be learning to squeeze the front brake lever, while also twisting the throttle and keeping the correct RPM with the same hand. This guy pretty much nails the explanation for the process, and if you follow the steps, you'll be a master in no time. I will reiterate one thing: You should really emphasize putting your weight over the front end to make sure the front wheel stays planted while the rear spins.
Unless you're drag racing, there's really no benefit to doing a burnout other than the joy you get from it. However, keep in mind that the longer you spin the tire, the flatter the middle of the tire is going to get. It can ruin a rear tire extremely fast, but it's hard to control yourself once you see the smoke rolling. The best timing for a burnout is when your rear tire is already getting near the replacement point.
You can't attempt to impress people unless you at least know how to burnout, so next time you're ready to change tires, give it a shot and have a little fun. It's addicting, take my word for it. Remember, there's a time and a place for burnouts, and make sure to stay safe out there on two wheels.