A friend of mine actually offered to give me my first makeover. It was really helpful. Once we got a look that I liked, she explained what she did and how she did it so I could at least get close to that look on my own.
Specific to the eyebrows, she said to do the top edge of the brows first. If you start with the bottom edge, it's easy to pluck too high and get more arch than you really need, as well as getting a narrow bit across the middle of the brow. With a finished upper edge, you have a better idea of when to stop. I also like the idea mentioned earlier of drawing in the shape with eyebrow pencil first.
I should buy stock in Sally Hansen; the facial waxing strips are perfect for cleaning up my unibrow.
Plucking/waxing will hurt less if you stay on top of your eyebrow maintenance.