Which hairs you tweeze and which ones you don't is the difference between attractively shaped brows and misshapen ones.
Try using an eyebrow pencil to draw on different shapes over your brow area to see which shape looks the best.
Use a magnifying mirror, at least a 5X magnification, so you can see each hair.
Go slowly (one hair at a time) so you don't over-tweeze.
The beginning of the brow should align with the center of the nostril.
The arch of the brow should fall at the back third of the eye.
The eyebrow should follow the length of the eye but it shouldn't extend into the temple area. The basic rule is that the front part of the brow should never drop below the back part of the brow. Allowing this to happen, either with the way you tweeze your eyebrows or the way you draw them on, makes you look like you’re frowning and overemphasizes the downward movement of the back part of the eye.
Avoid over-tweezing above the brow. A few stray hairs are fine to remove, but too much and it can create an unnatural look.
Do not overstate the shape of the brow; minimal brow alteration is best.
Do not pluck brows into a thin line thinking it will make your eyes look larger. It can look dated or give the face a surprised look and this shape is not easy to correct once the damage is done.