Some tips regarding sideburns:
1. When they start to get grizzly and you reach for the clippers, always put the largest number guard on first, then trim. If they are still not tamed to your liking, move down a guard size and repeat. By starting off with the largest guard, you are still left with some length to trim if required; the only thing a too small guard leaves you with is regrets.
2. When squaring off the bottom of a sideburn, use your ears. Pick a landmark like the bottom of the ear, the place where the lobe begins, the midpoint, etc and start shaving down from a little below the landmark. Then you can return back to the landmark to even it out a bit. Using the landmarks will keep your sideburns symmetric unless you have drastic differences between your left and right ears in terms of shape or position. Also, when evening out the bottoms, hold your head at its normal resting position. Tilting your head to bring your sideburn closer to the mirror usually results in the bottom of the sideburn having a tilt as well when you return your head to its natural position.
3. When picking a length, pay attention to your hairstyle. The longer your hair is, the lower you can go with your side burns. Sideburns that go below your ear look silly if paired with a buzz cut. Also the length of the hairs in your sideburns should never be longer than the hair about the ears. So, if you are using a #3 guard for the hair around your ears, use a #3 or lower on your facial hair clippers as well.
