Grab Some Tweezers
Nothing against the legendary Andy Rooney, but most of us should steer clear of bushy, 1-inch-tall eyebrows. Pam Anderson's millimeter arches are a pass, too.
Getting to the right eyebrow can be tricky. If you've got plenty to work with, you're less likely to pull a single hair with uh-oh results, but you're more likely to grab the wrong strand. Naturally sparser brows have better-distinguished hairs, but every pluck had better be extremely well-planned.
Before you pick up your angled tweezers, brush your brows upward. This clearly reveals the line you're working with so you don't accidentally create a gap (which can lead to ultra-skinny in an effort to even-out). As you pluck, keep your ideal shape in mind, and check your work after every few hairs to make sure you're on the right track.
You can pull the top ones, too, if you want to lower an arch or remove an overly pointy peak. In this case, brush your eyebrows downward before you start.
Do work with care, but a misstep isn't a tragedy. If you pull something you shouldn't have, don't sweat it. Simply proceed to the next step.