You have to decide the shape of eye brows that you want at first. There are general rules for common face shapes and eye brows.
High Arched shape:
This one is most popular among women because it gives a regal touch to the face and is very attractive. It goes with nearly all face shapes. High arches kind of open up the eyes.
A low arch is good for people with smaller foreheads since it gives an illusion of longevity to the face.
The angular shape best fits those with round faces and helps balance the all round effect
Women with big round eyes can look like absolute show stoppers if they top them up with rounded eye brows..
Get rid of stray hair:
Brush your eye brows in upward motion and trim any stray hairs.
Deciding where the eyebrow should start and end takes a bit of measurements. Take a ruler and place one end on the outside of your nostril and the other on the eye's inner corner. Where the ruler intersects with your brow, it is the starting point. Do this for the outer side of your eye and use the intersection to determine the end point.
Find the arch:
Determining the arch is the most crucial part. Hold the pencil to the side of your nostril and connect it to the outer edge of your iris. This is the highest point of your arch.
Pluck the hair from the bottom to the peak point of the arch. Work on the tails by plucking/tweezing the hair. The distance in the middle of your brows should ideally equal the length of your eyes.
Once you get the basic shape, maintain your eyebrows by plucking stray hair regularly. Getting the perfect shape is difficult. Once you get it right, you can always always follow the outline and maintain your brows.
Go to a beautician to get your eyebrow shape perfect. Once you have a shape that you goes with your face, all you have to do is maintain it by plucking unwanted hair and keeping the original shape.