this would vary a great deal on your total body mass, gender, position in the company, etc.
As a truck driver (CDL) I have a lower limit allowed me.
I therefore learned to have a quick couple of alcoholic beverages upon arriving, then switch to a nonalcoholic, but "acceptable looking" beverage. Because here is the really crazy making thing: You probably do better by looking like a reasonable "social" drinker, than by coming off as a total teetotaler, or a raving drunk.
So---bearing in mind at all times that you ARE being evaluated at every moment of this encounter----either do not drink alcohol, but appear to (Ie, ask the bartender to give you an "innocent" drink, but pay and tip as if it had alcohol)---or---if you truely are one of those rare individuals who knows your limit and can stick to it, drink that early on, thus "relaxing" and showing you are a social drinker, then becoming sober enough to drive safely after you switch to the virgin variety of your favorite drink. It is always admirable to confess to the bartender that you are the "designated driver" In some cases they will then give you your drinks for free. (You should still tip if you want to be classy.) this is a difficult area. Persons who do drink often feel "judged" by those who pointedly don't. the reasonable answer is to drink no more than you would feel good about having cleared from your system before driving home. If at an "exotic" setting such as a Vegas "seminar"---the reasonable amount to drink is that amount which will not cause you to wake up with either a severe hangover, or a complete stranger who also works for your company. Remember---this is work, not play, no matter how carefully it is disguised.