If you want an arch for example, gradually pluck hairs so that they peak a bit in the middle of the brow. Then tweeze the hairs so they get progressively thinner until they end and only a few hairs remain. Fill in the sparse brow with eye shadow or eyeliner. Both will add color and dimension to give the illusion that your brows are fuller and darker than they naturally are. For course and unruly hairs, you may consider seeking out the help of a professional who can either wax or pluck your way to ideal brows.
Thick brows can seem unmanageable and it's best to pluck the stray hairs under the brow first.
Then start at the thickest part of the brow and tweeze particularly curly or course hairs. Work towards your desired shape and take caution not to over-pluck just because there are so many hairs. To smooth and tame thick brows, apply a dab of hair gel and style. Without a tight grip, the tweezer will never be very effective grabbing unwanted hair. Pluck hairs in the direction that they grow.