keep fully hydrated_will also help keeping the little fella standing tall and proud-zinc,magnesium,could try horny goat weed...i know in high enough doses it keeps me going and adds to the volume.usually any of the OTC things like Wrecking Ball or other volumizers work fairly well.the more goo the more you'll feel like it's never going to end which is a good thing.
there was this one thing a few years back advertised in the back of mens magazines like FHM,Mens Health,etc...called "The Ropes".never tried it but it always got great reviews.