With the magic of the Internet, you no longer need to find someone in your area. The world's best authority on coats of arms is the College of Arms, in London. You can read all about them on their web site, below.
What follows is longer and better written than some answers, Politeness dictates I didn't write it all, just now, just for you.
My source is
http://college-of-arms.gov.uk
and, in particular,
http://college-of-arms.gov.uk/Faq.htm
Crests are the top part of a Coat of Arms. If you have a coat of arms, you typically put just the crest on your personal stationary and have someone carve it into the stone above the front doors of the family estate.
A "family crest" or "family Coat of arms" is "Family" in the sense of "My family estate", not in the sense of "Everyone named {Carpenter, Miller, Smith ...} can use it".
Individuals earn or buy a coat of arms. Anyone who is an English subject, of good character, and has done something notable can "apply", and I get the sense that, in these days, unless you've robbed a bank, the college of heralds will look favorably on your application, so long as you've included a "cheque" [That's how they spell "check" there]. They cost about (US) $7,000 the last time I looked.
Once someone has one, his eldest legitimate son inherits it. His other legitimate sons are strongly urged to pay the college of heralds to create a variation, or to stop using it. Women and illegitimate sons are too complicated to deal with here. In traditional English families, the oldest legitimate male heir inherits the bulk of the fortune and the family estate. If he is a nice guy, he’ll let his siblings have a small apartment in it, and loan them a housemaid or two as needed, but it is his, not theirs.
So, in most of the English romances or murder mysteries you read, someone is always popping down to the "family" estate for the grouse season, or receiving a note on engraved stationary with a "family" crest at the top, or driving away in a 4-horse coach with the “family” coat of arms on the door. Note again, estate, crest and coat of arms belong to one line in one family, not everyone in the world named "{Carpenter, Miller, Smith ...}". But, that is where the myth of a "family" coat of arms originates.
House of names -
http://www.houseofnames.com
will probably show you a Coat of Arms, with a crest, that was (probably) once issued to someone with the same surname as yours, but they make their profits on the gullible. They do their best to convince people that everyone named "{Carpenter, Miller, Smith ...}" has the same coat of arms, and they happen to have it, tastefully done in porcelain and mounted on a walnut plaque, for $39.99.