In this video from livestrong, Joe Ann Ganci, a barber, teaches how to trim a beard. On a goatee use a smaller clipper. With a comb, clean up the edges of whatever is hanging out. Comb it to the side and make a nice clean line underneath and along the edges. There are several different clippers you can use depending on how thick the beard is. Make sure your edging is nice and make sure the length is right. If you don't want to take too much off of the beard or goatee, you put a bigger blade on the clipper.