I second the Pimsluer basic course. It will get you started and they explain the tones and it is very clear how you are to pronounce a word.

There are also people who will tutor you via Skype for something like $15-20 USD for a 30 min session.

Once you get to China you will start to get used to hearing the language spoken which is a big part of learning to speak the language.

As for me, I keep my expectations low.