Growing a beard takes no skill (just genetics), but maintaining it requires some practice. Letting your royal mane grow wild and prosperous is great, however, there will come a time when you'll will need to trim your beard, neck, and cheek line.
What you need:
Step 1: Find Your Neckline
1. Imagine a curved "horse shoe" like line between both ears. Place two fingers above your Adam's apple (a) and turn your neck to each side. Trim all straggler hairs visualizing the line (a)
Step 2: Find Your Cheek Line
2. Always follow the natural curve of your cheek line (b) from the top of your sideburns (mid-ear level) to the beginning of your mustache. Add some shaving cream, then shave your check line (b) following the natural curve. Always keep your cheek line as high as possible. Proceed to add shaving cream to your neckline (a) and shave with smooth downward strokes.