Good brows are essential for good makeup. There are currently a few fad trends making the round- like squiggly brows or "Christmas tree" brows. Fads aside, generally artists will use two brow techniques: Natural "boy" brows and the sculpted Instagram brows. At the end of the day the type of brow you place on a clients is dependent on the client.
Personally, if a client leaves it up to me, I prefer a mix of both brow types. I like to sculpt (outline) the brow, especially the tail end, and the front to middle, I fill in like boy brows.
Boy Brows - This is the most natural of the brow techniques. It is not heavily dependent on pomades and relies more on a precise brow pencil and/or powder to essentially fill in the brow. An artist uses hair like strokes to fill in any sparse areas and trace (lightly) around the brows. This style doesn't need to be "neat" because the goal is for the brow to look as natural as possible. Charlotte Tilbury, a megastar in the Makeup & Beauty Industry, is well known for her natural brow technique. Client-wise, this techniques is best for people with really thick brows or people with average brows. If a client has barely any brows, I would shy away for using this technique by itself. If you would like to try it I suggest outlining the brows with a pencil and then using a pomade with a very thin brow brush (like MAC 208) and hair like strokes or using a powder to gently fill in gaps. Editorial and Runway makeup typically uses this brow style.
Sculpted Brows: Sculpted Brows are beautiful. They're ultra glam, super neat, and adds a finish look to the eye makeup. These brows are typically achieved by using a pomade or pencil to outline. You can fill in the entire brow with the pomade but the front of the brow should be left bare. Most artists I've seen usually blend the pomade using a spoolie to add some coverage to the front of the brow and either leave it like that or use a pencil to make hair like strokes in the front. TailorMadeJane (IG), a Las Vegas Makeup Artist, is one of my favorite pro artists. Her sculpted brows are neat, thick, and blended to perfection!
I love the neatness of the sculpted brows on the ends and the naturalness of the boy brow in the front. I also use powder to do most of my filling in. You can use powders for either the sculpted or natural brows, but this is where the quality of the products you use stand out.
I have tried many a brow pomade and pencils galore. I don't consider myself a makeup snob because any good makeup enthusiast knows that cost and quality are mutually exclusive. However, and by far, Anastasia Beverly Hills, makes some of the best brow pencils you can find. I've been trying to find a cheaper alternative dupe from brands like NYX, MAC, LA Colors, etc. but nothing compares. Benefit and Anastasia literally win by a landslide because there pencils work great over hair. Pomade wise, the consistency of the Anastasia products are in a league of their own.
There are tons of artists with brow tutorials on Youtube (my own is coming soon), so find someone whose style you like and watch their technique. Most importantly, have fun!!