Anybody have any surefire ways to boost their sperm count/viability?

Trying to get accepted to a sperm bank as a donor, I already got pre-approved on profile, just need to go in and wank one out in 9 days for analysis.

I'm gonna hold off on jacking it to hopefully boost my sperm count, but outside buying multi-vitamins or zinc supplements, I'm not sure what would give me the best odds for viable sperm, scientifically speaking.