I am repeating myself here but I really believe that you should learn the basics (the proper speech) first, THEN you venture off to find your own style.
Many beginners make the mistake of trying to imitate what they see/hear in places like Movies, Pop Songs, Internet Chatrooms/Message Boards... If someone wants to talk/write in Japanese laden with slangs and informal expressions, fine. It is her/his choice. I just hope that it is a choice made by someone who understands very well how it would sound and be perceived by others in that particular Time, Place & Occasion and NOT a choice made because there are no other choices, because that's the only way they know how to say it.