After receiving your pour, get out of the way – don't shuffle, walk.
Do not wear white.
If you must wear white, and you spill red wine on it, immediately splash the stain with white wine. And don't forget to get out of the way, preferably in the method described above.
Do not wear perfume or anything else that smells up the room.
Talk, don't holler, but keep your travel stories to a minimum; we are there to taste the wine in front of us not the one you had in Europe, the name of which you cannot remember but you seem to have all night trying to recall.
If you know nothing about wine, don't use this forum to dump a pile of questions onto the table for the pourer to answer, who may know less than you and will give you a bad answer anyway. Taste the wine (and get out of the way). If you like what you taste resolve to take a wine course later.
A common complaint heard at wine tastings: "this wine tastes metallic." Leave your tongue ring at home.
Forego the lipstick too.
Most wine tastings include a buffet of some sort. The food is there to eat, but don't be a hog. Also keep in mind there are hundreds of people behind you. This is not the time for indecision. Fill your plate and get out of the way – see number one for instructions.
It is common knowledge among wine professionals that one should drink a glass of water for every glass of wine consumed. This practice prevents you from becoming dehydrated and maybe from getting drunk. The water cure has an added advantage: it helps to thin the crowd every so often, shifting the bulk from the tasting floor to the waiting line at the toilet.
Leave the wineglass and the buffet dish on the counter/s provided for them – do not leave them in the toilet.
If you reject the water treatment but want to prevent yourself from getting drunk learn to spit, preferably in the spittoon provided. Under no circumstances should you spit in someone's face, intentionally or not. In fact, if you must talk to your neighbor, stand a few feet apart; people at wine tastings who do drink a lot of water tend to release the water between toilet trips by spraying droplets when they speak.
If you attend a wine tasting for the sole purpose of putting on a free drunk, make an appointment with your counselor to talk about it. But if you are unsuccessful at reaching your counselor and so you attend the wine tasting instead, do not leave your coat at the coat-check counter. What with the increase in crowds at these events, it is quite difficult to get your coat back under the best of circumstances.
If the wine tasting is a consumer event leave your business cards home. People who engage in business discussions rarely remember their etiquette and so they take up valuable floor space. If you must give out a business card, be discreet and be quick about it, and be sure the recipient wants the thing.
If you are in the wine business and at a business-oriented wine tasting, you are likely impervious to the requirements of proper etiquette, so do whatever you want, but do get out of the way.