Can an athlete do anything to make themself more resistant of concusions?

Resist concussions: Yes. Use the most sophisticated protective devices to protect the head from injury. Keep in excellent physical shape so as to protect yourself from injury. Do not participate in dangerous activities and avoid alcohol and other drugs that could make you be careless and more prone to injury.

Training, equipment: An athlete can use the best head-protection gear (must fit him properly). He needs to have eyes in the back of his head (helmet) and know what is happening 360 degrees around him (some of that is natural talent, some is training). He has to be fast to protect his head when he senses a direct hit coming (again, some nature, some nurture). He must stay hydrated and keep a sharp mind and a sharp eye.