The following "A, B, C, D" rule is a convenient guide to the sort of moles which should be checked out by a doctor.
Asymmetry - one half unlike the other
Border irregularity - rough or poorly defined edges
Colour variety - from one area to another, shades of tan and brown-black and sometimes patches of white, red or blue
Diameter - larger than 6mm or is growing bigger
HOW TO BE SUNSMART
Cover up:
Wear a wide-brimmed hat or a hat with a neck flap to protect your neck
Wear a T-shirt or other shirt with a close-weave material.
USE SUNSCREEN
Use sunscreen with a sun protection factor (SPF)15 or higher
Make sure it has UVA and UVB protection
Put sunscreen on 20 minutes before going out into the sun
Use lots of sunscreen and reapply every two hours (more often if you have been swimming).
SEEK SHADE
Avoid being out in the sun between 11 a.m. and 3 p.m.
Use sun umbrellas and other types of shade to protect you
PROTECT YOUR EYES
Wear sunglasses that give a high protection against UV rays (European Standard EN 1836 or BS Standard BS 27 24 19 87).