Select the language you want to learn and start with the difficulty level that corresponds to your skill level. If you're not sure which level to choose, it's best to start with the first level. Even if it repeats some vocabulary that you already know, you'll get a refresher course in the language's foundations. Don't select a higher level if you're not experienced with the language. You'll get frustrated and won't reap the benefits of the software.
Stick with one language at a time. It's easy to become excited about learning new languages and want to try several at once, but you may become overwhelmed with information and forget which grammar rules apply to which language. Immerse yourself completely in just one language at once so that you can focus all of your attention on it.
Use the software every day. The key to learning a foreign language is to expose yourself to it frequently. If you only use your Rosetta Stone software once a week, you'll have a hard time remembering what you learned in previous weeks and won't be able to build upon what you know. Complete all of the software's components, including the interactive lessons, games and quizzes.
Supplement your Rosetta Stone software with other forms of learning. Watch television and movies, listen to music and read children's books in your selected language. Practice speaking the language in conversation with people who speak it and frequent restaurants that serve the language's cuisine so you can order in the native tongue. Travel to a country in which your language is spoken if you can.