The best way to do this is by using a trimmer with an adjustable blade. Start with the longest setting and work your way down until you get the desired look.
Start by trimming an inch above the jawline with your blades set to one setting shorter than the rest of your beard. You should trim an inch towards the sideburns. Sideburns that extend to the bottom of the ear can help offset a long face.
How Do You Fade Sideburns On Your Beard?
Start by trimming an inch above the jawline with your blades set to one setting shorter than the rest of your beard. You should trim an inch towards the sideburns. 2. After shortening the blades, trim another inch towards your sideburns. 
How Do You Groom The Side Of Your Beard?
Start around your chin and trim away loose ends. If you take an equal amount from the opposite side, symmetry is important. Continue up from the bottom of your sideburns. If you are trimming a beard with scissors, make sure to comb against the grain. 
How Long Should Sideburns Be With Beard?
It’s a general rule that they shouldn’t extend much further than the middle of your ear. Sideburns that extend to the bottom of the ear can help offset a long face and help a round face look less so. Shorter sideburns that hit mid-ear look good if you have a weak chin. 
Should You Trim Sideburns When Growing Out Hair?
Sideburns tend to grow out instead of down, and it feels like they can get out of control very quickly. It’s a good idea to trim your sideburns as you grow your hair out to keep things under control. 
Frank Harmenstein is the lead editor of the grooming website Cut Throat Straight Razor, and has over 15 years of experience in the industry. He’s personally tested and reviewed over 200 different straight razors, and has written countless articles on the subject.