40 years old and I'm going to try to grow a full beard for the first time in my life. Wish me luck.
Do not shave at all for at least the first four weeks of growth. One of the most common errors is to attempt to start shaping or sculpting the beard too early in the process. Even if you are just planning to grow a "Van Dyke" or goatee, you should let everything grow for the first four weeks. WHY let your beard grow for four weeks before you start to shape it -- even if you are just growing a goatee? If you don't wait, you might cut off more than you really wanted. Also, you might not have thought about going for the striking effect of an oversized goatee. You can always trim it down to a smaller size later.
My advice: when I start to grow my beard I choose a line between my chin and neck, and keep it shaved below that. This cuts down on the itchiness and keeps it looking neat while it grows. Enjoy!