How are these so called 'baristas' ruining my coffee, and how do I make them stop?

I wouldn't harangue the baristas about this. Write to the company, if it's a large chain, or talk to the manager and explain what's going on. Those are the people who control training and quality assurance. In my experience, they care a lot about customer input. Particularly if you note that you're telling other people about your experience. Rather than telling the baristas how to make your drink, taste it while you're still at the cafe and if it isn't right, take it back and ask for another. Specify what's wrong. ("Sorry, this is too weak. Can you make another?") But I wouldn't stand there telling them how to do their jobs...pissing off the people who handle your food isn't a great idea.

If you're getting inconsistent drinks, there are only two options: 1. Poor training. 2. Poor maintenance. Neither is anything you, the customer, can fix. The best that you can do is leave a complaint with the manager so that they know there's a problem, and get your coffee elsewhere. I would be absolutely clear in the complaint that you consider it the manager's, and not the employee's, problem, because these kind of issues are systemic. Don't make it easy for the manager to just yell at the employee who happened to be on shift. The truth is that training and maintenance cost money, and as long as the public accepts a bad cup of coffee, managers have a financial disincentive to let them slide. Some managers won't let that happen because they take pride in their product, but that's certainly not everyone. If you can't find a good coffee shop that's convenient, I would pick the least worst and attempt to go when it's not rush hour. When it gets busy, it's harder to make a good drink, and the last thing you want to do is remake one because you made a mistake. You maximize your chances of getting a good drink if the baristas have time to pay attention to what they're doing. (Now, I said "inconsistent" because it's possible that a place will do their drinks in a style that you don't like (by using darker/lighter beans than you prefer, for example). But if that's the case, then your drinks should be consistently bad.)

If it's a matter of different chains or different cafes - there's a strong possibility that you just don't like the espresso blend they serve. The best cafe in my neighborhood for relaxing with a cup and a newspaper happens to always serve bitter espresso. I suppose it's possible that they simply don't know how to pull a shot, but it's telling to me that they use a slightly weird brand of beans. My favorite cafe in the whole city roasts their own, too. So my guess is that it has to do with my palate and a specific preference for a certain sort of espresso blend. Of course if you're going to the same chain and some of them are getting it right and others aren't, then the issue is a technical one, not in the beans.

If you have an iPhone, is there an app for rating coffee places that could direct you to better places? I know there are such apps for my city, but then, Melbourne does think that it is a city that likes its coffee. As identified above, there are so many factors that go into coffee making that it is hard to narrow it down to technical or personal factors at a quick glance. My regular cafe had good baristas, but there was one particular one who just couldn't do it, so I would go elsewhere if I saw they were at the machine. I highly recommend listening to the http://www.coffeegeek.com/podcasts/cgpodcast.xml (also in iTunes) if you want to learn more. In one podcast, I remember them talking about how to find good coffee, and that one of the tips was that when you walk in, you should be hearing grinding because good places will grind fresh as required. I think it talked about other sounds and sights... but I don't remember which of the podcasts this was in!

They're steaming the milk too hot, at least that's my guess. I think when I was a barista, it was preferred to have it top out at 110F or so, where it was easy to pull it from the steamer and still have it go up to a scorching, shitty-tasting 120F. I might be wrong with the numbers, but just give your barista the heads up not to make your milk too hot. I wanted to come back here and correct myself, now that I've woken up, had half a coffee and seen some more realistic numbers. These numbers are waaaaay off, and obviously the issue of you often having an americano... Sorry for the useless, knee-jerk first response in the thread.

It's the length of the espresso shots, if they run too long they will taste bitter and foul.

If you're in London, chances are - as with most minimum wage jobs - your server is not a native English speaker and an angry lecture on the specifics of coffee making will not always be easily or happily understood. Also, if my experience in low-paid jobs is anything to go by, they've been told to do it *this way* and if they don't, they need to find themselves a new job. My advice is to try and find a local independent - you don't say where you are but there are lots of them about. Or buy a Gaggia and a commuter cup.

Assuming the barista is pulling decent shots to begin with, the easiest way to screw up an Americano is with the temperature of the water added to it -- it needs to be between about 195F and 205F. Hotter, and you'll have a burnt taste, colder, and it will be sour. This is a whole lot harder to ignore in an Americano than a milk-based drink, because just a little milk or sugar disguises it nicely, so a lot of places get it wrong. Around here, Starbucks (yeah, I know -- rules out the decent shot question right up front) has a tendency to pull the shots and then pour in water right off the boil, complementing over-roasted coffee with a burnt shot. Yum.

I hate to say it, but the best way to solve this issue is brewing your own. You can tweak it and make it exactly the way you want. When it's wrong, toss it and start over. http://www.amazon.com/exec/obidos/ASIN/B000F49XXG/metafilter-20/ref=nosim/ a great machine I own. It's cheap and makes a pretty good espresso. Barring this, find a place with a barista that makes your americanos correctly. Make friends with the barista and find out when they work. Only go when they work and ask them what they do differently than everyone else that makes your coffee so good.