Agree with PP, it's really about making sure you have nothing to regret if you get a negative. With the powerful drugs they're using, I'm not sure a little bit of this or that here or there is enough to determine a result one way or another.
That said, I feel like I need to know that I've done EVERYTHING I can to support success. Given what I'm spending on IVF, lifestyle/diet changes don't feel like a sacrifice at all.
I'll say one thing about alcohol--acupuncturists are vehemently against it. It's not for fear of harming the baby, but that it may interfere with fertility and the effectiveness of the cycle.
Dropping alcohol when I started TTC has been a gift regardless, I just feel so much better. Less dehydated, less headaches, cheaper dinner bills, less calories/sugar, and now I don't really enjoy it anymore anyway. I manage to have a great time while being a teetotaler.