For starters, DON'T take it when you're drunk.
I'd suggest starting with 1mg (so half of a bar)... Just swallow the pill, don't bother trying to snort it, snorting Xanax doesn't improve or strengthen the effects of it one bit (if anything, it does the opposite). Xanax starts working quite fast (about 15 minutes after swallowing it). Wait like, at least 20 minutes (ideally 30 minutes) to see how it effects you, & then if you want to take more (which I'm sure you will, if your goal is to get as "fucked up from Xanax as possible), take another half milligram (so, one fourth of a bar... or one half of the half of the bar you'd have left, since you'd have already taken the other half of the bar already). Wait like 20 minutes, & then take the rest of the bar.
The reason I suggest doing it that way is because it's not uncommon for people with pretty much no Xanax tolerance at all to just pass out after taking a whole bar at once, or even by taking less than a whole bar at once. & if you're simply asleep the entire time you're on the Xanax, then, well, that's a pretty good way to totally waste it.