Teach Yourself
If you've got the motivation and the self-discipline, you can very easily teach yourself a foreign language - especially these days, when there are all kinds of CDs, DVDs and websites to help you on your way.
Give it time
Virtually all teach-yourself courses are out to persuade you that language-learning is easy: you can become fluent merely by listening to a tape for ten minutes a day, while doing the washing up, or even while you are asleep. Don't you believe it! You are going to have to work at it, regularly, and with your full concentration. You may be able to learn the basics quickly (always impressive to those who speak none of the language at all), but it takes dedication to learn a language to a more advanced level of competence. This does not mean it has to be uncomfortably hard: if you choose the course that is right for you, it can be entertaining and rewarding. But you are going to need to give it some time.
The right course for you
Taking on a language course of any kind is quite a commitment, so it is vital to choose one that suits you. Be warned: some teach-yourself courses are not well constructed and are as dry as dust. You want a course that you can enjoy, and which is at the right level for you, otherwise your enthusiasm will wane and your expensive box-set will sit on a shelf gathering dust (the fate of so many language courses!) If you want to teach yourself a language for use on holiday, find a course geared to that kind of language usage - a course to tells you how to order another bottle of wine, not one that devotes hours to the use of the subjunctive tense in expressions of probability. Ask your friends if they have any recommendations for courses they have followed, or check reviews on the Internet. And remember, because you pay more, it doesn't mean you'll necessarily get better quality.
DVDs and TV
Look out for language courses that include film. These place the language in a real, life-like context, and the visual images help to reinforce your memory of words and phrases.
See www.bbc.co.uk/languages
Self-discipline
It is important to impose a timetable for learning: to make progress you are going to have to set yourself a target and stick to it. Some people prefer to do half an hour every day; some will do a three-hour session once, or twice, a week. The important thing is not to be over-ambitious: if you set yourself too onerous a regime, language learning will rapidly become a chore, and you will abandon it. If self-discipline is not your style, then simply set a start time, and say you'll just do ten minutes: the most difficult thing is getting started, but once under way, ten minutes easily becomes half an hour, if not an hour.
Accents
Correct pronunciation and accent can be a problem when teaching yourself a language, even with CDs and repetition exercises. Some of this may be down to natural ability: some people have 'an ear' for language, and can adopt a foreign accent effortlessly. Others may learn all the grammar and vocabulary needed to speak a foreign language, but their accent makes them almost unintelligible.
Acquiring a good accent requires a mixture of careful listening and practice, but perhaps also a bit of play-acting. Remember that every language has its favoured part of the mouth and throat, and you have to adopt this, even if it feels quite different to English. In other words, act the accent. A good way to start is to imagine native-speakers of the language you are trying to learn, and think of the kind of heavy accent with which they might try to speak English. Try imitating that: this will show you their favoured part of the mouth and throat. Now try speaking their own language in the same style.