Alcohol

What rules does everyone follow when drinking and breastfeeding/pumping? I've seen to wait 2 hours per drink, 4 hours per drink, some say if you feel sober enough to drive you can breast feed, others say the highest concentration of alcohol is 2 hours after drinking so wouldn't that be the worst timing then? Also, when is it safe to have a drink, when the baby is how old? Some say 3 months, some say 6 months, but if you follow the right rules, does it even matter? And before anyone gets defensive, I'm talking about a glass of wine or beer. Not trying to get drunk or crazy