1: England and Wales

Note that this only applies to England and Wales, not other parts of the British Isles, where there are subtle differences.

Where: Pubs and bars. A pub is a "public house", normally an establishment dedicated to drinking with a characteristically pubbish name such as the George & Dragon or the Chequers Inn. Bars come in various flavours such as wine bars (fairly posh), just generically hip bars which aren't pubs (you'll know when you see them) and more standard things like hotel bars.

Seating: Seating in pubs is entirely self-assigned - tables are there, but nobody will tell you where to sit. If one is free that's great and you can sit there, if not, tough. If there aren't enough chairs for your party it's fine to see if other tables have chairs they aren't using ("Excuse me, is anyone sitting here?"). You can sit at the bar if you want, but you may irritate other patrons if they find they can't get to the bar because you're in the way.

Bars are somewhat different, and you have to play it by ear. Some of the more pretentious ones will insist on seating you, but that's considered kind of weird.

Service: In pubs, entirely at the bar. You can sit at a table all you want but nobody will come and serve you. Walk up to the bar and order there - the rule is 'first come, first served'. A common mistake is to try and form an orderly queue. This won't work - everyone at the bar will, in general, know who was there before them and give way as appropriate - it's considered extremely rude to allow yourself to be served when you know the person standing on one side of you has been waiting longer. If that's the case, the words "I think this (lady/gentleman) was before me..." will make you friends.

What to order: If you don't know what else to have and want to try some local beer - "Pint of bitter, please". Many pubs will have multiple variants of each type of beer - bitter and other ales usually come out of big hand pumps (the pump lever pulls the beer out of the cask without the help of additional gas), while lager and the like are served from smaller taps under gas. If there are multiple real ales on offer, indicate which one you want by naming the brewer ("Pint of Everard's") or the beer itself ("Pint of Summer Lightning"). If you're really confused, it's perfectly okay to just point at the pump for the beer you want. If you have no opinion, the pub will usually help you out if you just ask for "bitter" or "lager".

Measures: For beer, pints (568ml) and halves (half-pints, 284ml). Spirits come in standard 25ml or 35ml measures, measured out by government-stamped measuring cups or optics (the things bottles sit in upside-down behind the bar).

Payment: You pay for drinks as you get them. Don't expect the bar to run a tab for you unless you've discussed it in advance and they've agreed to do it - people don't generally do this unless they're buying drinks for a lot of people over the course of the evening. In general, expect to be on a round system (everyone at the table takes their turn to get a round of drinks).

Tipping: Never with money. If you leave money on the bar people will assume you forgot your change. It's okay, if you get on well with a particular member of bar staff, to add ".. and whatever you're having" to your order. This usually means they'll add the price of a half of something to whatever you just bought, and although they may not take the drink right then, they will do so later. This is very much the exception rather than the rule, though, otherwise bar staff would all be permanently plastered.

Caveats: Mind your Ps and Qs - "please" and "thank you" (or "thanks", "cheers", etc) are essential for lubricating the wheels. If you don't say "please", you'll be considered rude and boorish.

Drinking age: 18.

See also: The definitive guide to British pub etiquette, Kate Fox's Passport to the Pub.

What?

I travel quite a bit. Everywhere I go one of the most basic rules is that sooner or later, I'll need a beer. The rules for getting served smoothly in pubs and bars, though, vary wildly throughout the world. My plan here is to summarise the standard rules of bar etiquette in all the countries I can find rules for, so others can avoid making idiots of themselves when visiting strange countries... when all you really want is a pint.