Beard hairs have a natural oil called sebum that helps keep them moisturized. The sebum and dead skin cells can mix and create an oily, crusty mess when you often don't wash your beard. Not only is this unattractive, but it can also lead to acne.
To avoid this, wash your beard with a mild shampoo at least once a week. You can also use a conditioner if your beard is dry or tangled. Be sure to rinse your beard thoroughly after washing and conditioning it, as residue from the products can make it feel greasy.
If you plan on growing a beard, start by trimming it down to a manageable length. A longer beard will require more care than a shorter one. Use a comb or brush to groom it daily, and invest in some quality beard oil to keep it looking healthy.