Sorry to say, but you'll be awkward no matter what when you first go over there, whether that be in the language or your cultural faux pas.
But, I would suggest getting a textbook, such as the Genki series. There are also tons of free alternatives online, one I particularly recommend is
Tae Kim's grammar guide. In my opinion he does a good job of explaining the finer points and has some good examples.
You may also want to try downloading a free flash card program called Anki. You can either make your own stacks or download tons of free ones people have made. They have stacks for JLPT vocab, kanji, sentences, etc.
Lang-8 is another good one. It let's you write diaries in the language you are learning that native speakers will correct. In turn, you can also correct their entries that they write in your native tongue.
Apart from all those I would just recommend immersing yourself in as much Japanese as possible, whether that be TV, music, newspapers, blogs, whatever. Keyhole TV is a free program that lets you stream Japanese TV. Naturally, you won't understand much at first but as you learn more you'll naturally develop your skills just from hearing the same phrases over and over.