Ahhhh the swirl. Gently rotating your glass with a modest pour of wine in it so it rises and falls around the sides of the glass...it's a little hypnotizing to watch. I won't lie to you- I love the swirl. Yes it looks rather pretentious when you're out, but man it does an important job, fast. And, lets face it, it's fun.
So the main reason we swirl wine is to aerate it. If you really think about it your wine has been a little cooped up. Let's assume that you have a recent vintage- perhaps even just a year or two old. In the grand scheme of things, that would be deemed a young wine. However, that means though that for a year or two, at least, that wine has been contained in that bottle. It's been sealed in, trapped. So when you free it from the confines of its enclosure- well, its gotta stretch its legs. Think about when you get off an airplane after a long flight and standing has never felt as good as those first few steps. Swirling your glass, letting air in, it mimics that sensation. It gives your wine a chance to breathe. That air you add to the glass is allowing the wine to open, and letting its flavors shine.
Swirling doesn't need to be done with too much gusto, a simple rotation will get the wine going. The big secret is that this can easily be done in two ways- either holding the glass in the air, watching the wine catch the light, or doing so with the base firmly planted on the table. Sometimes, with red wine, that's the safer choice unless you're feeling like your dry cleaning bill has been a bit low lately.
No matter which way you choose to swirl - always do so. Allow that wine to breathe, stretch its legs, and makes it ready for your consumption.