If you are no more of schoolage, you can still choose to take language classes. My advice is : avoid group classes at any cost. They are a waste of time, unless you are at a very advanced level. You'd better save some money to buy good tapes and private lessons when you are more advanced. To tell you that there are three word genres in russian, or that you put s at the end of words in spanish to denote plurality, you don't need a teacher. With a good book, you'll be able to learn at your own pace, re-read what is difficult for you, browse through the easy parts, etc... All this at midnight or on Sunday if you want. Which classes are that convenient?

Some people say that they would not study if they were to do it on their own, that the regularity of the class helps them win over their laziness or lack of will. This is NOT sufficient. Unmotivated or lazy people will never master their target language, classes or not.