Wax the string and cables once every week or so. Any time they feel dry, wax it. Wax it before shooting in wet/rainy conditions to help keep water out of the string. Then wax it again the morning after shooting in the rain, making sure the rigging has dried out. I'd even wax before shooting where it's dry and dusty, to keep the dust from getting between the fibers.

After waxing, rub the string briskly with a piece of soft leather, to heat the wax and help it flow into the string, instead of just sitting up on top of the surface fibers. It'll also burnish the wax, to help keep dirt and water out of the string.