"I'd like to learn a language, but don't really have the time." Does that statement sound at all familiar? If so then read on.
Carpe momentum - seizing the moment
During a typical day, there are usually times when you could fit in a bit of language study. Even if you only study for five or ten minutes at a time, it all adds up in the end. In fact it can be beneficial to spread your studies over a number short periods, rather than doing it all in one or two big chunks. The more often you practice and review material, the better you'll remember it and be able to use it.
If you commute to work or school/college/university every day, perhaps you could use that time for study. Other times you could use for study/practice include while preparing meals, washing dishes, doing house work, gardening, jogging, queueing, during your lunch break or at the gym.
The type of study or practice will depend on what else you're doing. In some cases you could listen to a lesson or two, or to other material such as songs, audio books, radio programmes, etc. In others you could practice reading and/or writing in your L2, or even practice speaking. If you want to practice your speaking in a public, perhaps you could pretend to talk on your mobile phone so that other people don't suspect your sanity and think you're talking to yourself.
Listen and learn
While working, maybe you could listen to online radio stations. Even if you don't listen to them very attentively, just having them burbling away in the background is benefical as it helps you to tune into the sounds and rhythms of your L2, and to pick up new words and phrases.
In a flash
Some language learners carry flashcards with them wherever they go, and whip them out whenever they have a spare moment. This can help you to learn vocabulary and grammar.
Putting your L2 to good use
Once you have reached an intermediate to advanced level in your L2, you might consider studying something else that interests you through the medium of the language. For example, if you're interested in the cusine of the country or region where your L2 is spoken, you could get some cookery books in the L2. This would enable you to improve your language skills, and to learn some new recipes at the same time.