A.C.
Double bra for extra support. Make sure your bra fits well and doesn't pinch anywhere.
Wear nursing pads even if you're past the leaking stage...my milk would often let down near the end of my work-out. It could be hormonal or related to the fact that milk glands are modified sweat glands...lol...a little gross, I know.
Pump or nurse as close as you can to starting.
Keep extra hydrated before, during, and after. Ensure that you keep up your caloric intake. Consider Mother's Milk Tea, Fenugreek, or adding oatmeal to help protect your supply.
I didn't notice so much difference with my supply but I also wasn't restricted my calories in any way.
Good luck.