See the videos carefully. I recommend you see the video sincerely cause videos describe many important matters about oDesk job profile and some essential topics. Here we tried to give a basic idea from the videos. You can find all the information about tests at Odesk Test Answers Page on the blog.
VIDEO 1: ODESK PROFILE TUTORIAL
VIDEO 2: HOW TO TAKE THE TEST IN ODESK
VIDEO 3: HOW TO BID AT ODESK
*Note: Writing a strong cover letter has been discussed at ODESK TIPS page of the blog
