Use beard balms to maintain moisture and health so it looks more full and less scraggly. Trim the sideburns and maybe chops every so often, as those are the main areas that will make you look homeless if they are unkempt.

Once you have some length, trim a half inch to an inch every 3-6 months (less often if it grows slower than that) to prevent and get rid of split ends, which can be a problem.