[steven]

I think a good way to learn how to speak is listening to people speaking Japanese. I'm sure you can read kana, but simply looking at the kana and trying to produce sound will not always be the answer. Rhythm, intonation, and dynamics are probably the most important thing for language. I think that's the reason you can usually understand your friends when they talk with their mouths full or do something similar in nature to that.

Imitation is important-- and the best way to imitate is to listen. However, like someone said before, the actual physical act of speaking is very important. It's basically muscle coordination. The sounds you make might sound right to your ears, but the more you listen, the more you will be able to hear your own mistakes. Your tongue has like a muscle memory for language and is set to English (I assume as that's what your message was written in) and has to get used to a new language.

If you have the means, record yourself and listen to your practice. I don't find it much different than practicing singing or other instruments for that matter. Just like music, rhyhtm and intonation are the biggies.