In Chinese Medicine the belief is that colds come on because the wind has entered the body. The point Gall Bladder 20 or Wind Pool at the base of the skull, just lateral to the SCM (the muscle you feel) is great at clearing wind. If you are feeling like you are at the beginning stages of a cold, you can massage this point for about 2 minutes. GB20 is also great to relieve headache, vertigo, pain or stiff neck, the common cold or runny nose.
Make sure to keep the back of your neck covered, especially at this time of year when the weather starts to warm up and one feels less of the need to have layers on.