There are a few methods of learning a foreign language with varying degrees of difficulty. Immersion is most often used in a classroom where only the language being taught is allowed to be spoken by the teacher and students. This method can be very frustrating to those who learn best in a slower, more methodical atmosphere, at their own pace. Perhaps a specific time requirement would be a factor in deciding if this method would work best for you. However, immersion provides excellent results if taught at an early age.
Certainly, much is to be said for any at-home system, where you can stop the audio portion as much as you like and follow along in the workbooks at a speed which suits you best. This method has perhaps a better selection of languages to choose from, and the best part of course is learning in your own time, on your own schedule.
In addition to these two popular methods, there are now a few websites dedicated to learning a foreign language easily, and they offer a wealth of free information.