I follow most of these things currently:

Omega-3s (Fish oil)--read Dr. Michael Lewis's protocol and book, When Brain's Collide. This one's easy: take fish oil. But make sure it's a good quality one.

Curcumin, NAC, polyphenols/flavonoids, HBOT, healthy food--the brain's metabolism doubles after head injury, MCT/coconut oil. The brain becomes unable to process glucose after injury. Ketones can prevent lots of damage, hence the MCT/coconut oil. Ketosis is a thought, but not a diet to be on long-term for most people and isn't for everyone.

A gradual return to activity--like Mark said above--following the 48 hours of little to no stimulus.

Exercise has also been shown to be beneficial.

If symptoms don't resolve after 6 weeks or so, look into other therapies--vision therapy, vestibular therapy, chiropractor, etc.

I've had this question myself, and this is what I have come up. I still have far to go in my recovery, but I feel had I done these things early into mine, I'd be in a different situation.

I got a long life ahead of me and though I don't plan on doing anything to get another concussion, accidents happen.