First, to get started, get started RIGHT. Many people start learning Japanese by focusing exclusively on romaji (which is the way we write Japanese sounds using the Latin alphabet). Do not do this. From day one, learn the characters and the correct pronunciation by using the Japanese alphabet from day one.
Second, make sure you focus on your grammar. If you don't, you will get off on the wrong foot with terrible habits. You will think you are saying one thing, when you are actually saying another thing.
Third, practice it wherever you go. Ideally, work with a live teacher every week, so you can actually practice real conversations.
As you continue, ask EVERYONE you know (who knows Japanese) to correct your Japanese. Always. It’s the quickest way to improve--via instant correction.
Finally, put together a solid study plan and schedule, using the many resources we have assembled for you on the pages to come. A great 'moving goalpost' is the JLPT (日本語能力試験 - Nihongo Nōryoku Shiken) system. JLPT stands for Japanese-Language Proficiency Test. This is the Japanese language proficiency test offered by the Japanese Ministry of Education, Culture, Sports, Science, and Technology. There are 5 levels: 5 is the basic level, whereas 1 is advanced fluency. Passing from level 3 to level 2 allows you to work in Japan in a Japanese environment. In other words, achieving level 2 is a huge accomplishment.
So to get started, your first step should be... to go to the next article!