Every linguist probably gets asked at least once a week what the best language-learning materials are. The answer really depends on what your goals are. If you are looking to get started with a language, looking to learn just enough of a language to get by on a trip, or are less interested in learning the mechanics of the language than in quickly getting up to speed, my best advice is to get a Pimsleur course.
Pimsleur courses are completely audio. Some courses do come with a small booklet designed to teach you a little bit about reading the language, but the majority of them do not, and the written materials are always optional. The structure of a Pimsleur course is that you are taught small phrases, and then drilled on them, over and over.
I have seen it claimed in reviews on Amazon that all Pimsleur courses follow the exact same sequence. Having done several of them, I can say that this is not true–the Farsi one is the only one that covers haggling, the Turkish one teaches you to ask for tea, rather than beer (a staple of the other Pimsleur courses), and the Swedish one goes on and on about how to say that you would like something to eat and something to drink. (More on that later.) Having said that, they do all seem to start the same way. You are taught a simple dialogue in which you learn to ask someone if they speak English, tell them that you do/don’t speak their language, and explain that you are an American. You are taught to say complex phrases by starting at the end and working your way back to the beginning. For reasons that I’m not clear on, that works quite well.
One of the things that amazes me about Pimsleur courses is that when I do them, I am almost always puzzled by why they teach you to say certain things–and then, when I get to wherever it is that the language is spoken, I find a use for them. For example, in the Japanese course, they drill you over and over on how to say “How much does this cost in dollars?” I couldn’t think of a single reason for this. Then I got to Japan for the first time. After a super-long flight, I was starved, and wanted a bowl of noodles before I left the airport. Problem: I didn’t have any Japanese currency. (This was before the advent of ATMs, which has made changing money almost irrelevant.) Ahah: I asked the lady at the counter of the noodle place “How much does this cost in dollars?” She told me, and I got my yummy bowl of noodles–mystery solved. The Italian one drilled me on and on with sentences like “is this Via Veneto? No, it’s that over there.” I couldn’t imagine why this would be that important, and then I got to Sardinia and discovered that an intersection was more likely to have six streets intersecting at odd angles than two, and figuring out which street you were on was, indeed, a challenge worthy of repeated conversations with strangers.
Pimsleur courses will give you basically no insight into the language that you are studying at all: they are just rote memorization and practice. However: if you follow the instructions, listen carefully, repeat everything that you are told to repeat, and attempt to respond to every prompt, you will be able to speak what you do know with confidence, to be understood by native speakers, and to understand the answers to your questions. This is huge–it is easy to learn how to ask where the bathroom is, but difficult to understand “all the way back, down the stairs, and to the left.” With Pimsleur courses, you will be able to do that.
Pimsleur courses are not all created equal. So far, I have done Japanese, Czech, Farsi, Turkish, Italian, Mandarin, and Swedish. The Swedish one was a disappointment–it went on and on about how to say that you would like something to eat and something to drink, long before it taught you things that are relevant and will need repeatedly (to the extent that you ever need to speak Swedish in Sweden, which is not very often, although it’s fun to see the look of surprise on a Swede’s face when you try). You are also not very likely to retain much if you don’t continue to use the language, but that is true of any instructional method. However, if you are looking to pick up some of a language before you go to a country, this is the method that I would recommend–you can do it in your car, and–most importantly–if you are just looking to be able to function, it works. In closing, here is a funny story about a conversation that I was able to have in Turkish, thanks entirely to my Pimsleur course–it’s way outside of what the course was intended for, but you will find that a little bit of a language can go a surprisingly long way, if you are creative: