What do sharks teeth look like?  I have never seen an actual fresh white shark tooth on the beach, but have found many fossilized sharks teeth. 
Color – for fossilized shark teeth, the color of the teeth will depend upon the materials in which the original teeth were buried.  I have found many of these fossils ranging in color from that of very light sand, to brown or gray, to pitch black.  In Onslow Beach, the teeth that turn up are largely pitch black.  In fact, when wet, they generally have a shine to them, almost like wet black spray paint.  For the Onslow Beach area, color may be the most important factor to target.   

Shape – Based on the movie Jaws, the cartoon character Mister Jaw, and what I learned from billboards, I began searching for triangle shaped objects.  It turns out that not all teeth are shaped like triangles.  In fact, most teeth I have found are not neatly triangular in profile.  Some internet research quickly revealed that the different shapes of teeth reflect different species of shark.  Perhaps more importantly, it is common for a portion of the gum to be attached to the teeth, which, depending on how much gum is there, can give the tooth a very odd and non-triangular outline.