Agree with the above point - shave with the grain - sometimes the grain on the neck hairs runs sideways, not always up / down. Just let your beard grow a little and check which way the hair grows - shave in this direction with a DE blade (check youtube for instructions from a guy called mantic (?)).
Prepare the skin prior to shaving, it may loosen an potentially ingrowing hairs and softens the beard for shaving.
Change the blade every 2-3 days (2-3 shaves).