Hello lala1739,
I've been told that men make their swimmers three months in advance so it could be good to be healthy around that time. A good quality zinc is supposed to be good too. I've also read somewhere that small amounts of caffeine can be good for sperm but not for us (sigh).
I've gotten a bit heavy with my partner in the past about not doing certain things but I think it just ends up stressing him out and making me annoyed. Now, I just do it silently by feeding him healthy food and buying him vitamins ... healthiness by stealth.
All the best for your upcoming ivf.