When pouring beer, you want to capture its aromas and get the right amount of head. The Art of Manliness suggests you can make that happen by aiming your pour at the middle of the glass.
Of course, the perfect pour isn't quite that simple. You need the right speed, and to bring the glass upward at the right time. The Art of Manliness explains:
Make sure you have a clean glass, and hold it at a 45-degree angle while pouring. Begin to pour your beer, and aim for about halfway down the glass. Don't be shy; if you're too slow, you'll end up with no head, and none of those wonderful aromas that enhance the flavour. When you tilt the glass upright, you'll notice the head start to form.
As you finishing pouring you should get the perfect amount of head. For lots of visual aids, check out the full post over at the Art of Manliness.
How to Properly Pour Beer [The Art of Manliness]