Contrary to the others, I think that if you get used to being able to use your dictionary quickly it can be a useful tool in the exam.
My advice to you would be to read as much Japanese that you can -- it doesn't matter what it is -- blog posts, websites, manga, kid's books -- and make sure you look up everything you don't know. Try to get ones with furigana in them though, otherwise you''ll have major problems looking things up. Like's been said, it is horrifyingly difficult at first but it gets easier. Also, I would advise watching movies, and tv shows and so on in Japanese. Yes, the manner of speaking is very casual, but you still pick up lots of good vocab along the way, and it improves your listening skills. Even so, it's probably more useful in the long run to learn how to speak in a more casual manner, if you have an interest in Japanese as a language rather than a subject, like I do.
Textbook wise, I cannot really advise you on because I must admit, I did not touch my textbook all year, out of class. Sorry bout that.