In these beginner levels, the most important thing you can do is ride accurately, as MIE has explained above. Often accuracy will win a test. Ride exactly to the letters, circles need to be circles with inside bend - if you are on a 20m circle, you need to have 20m circle bend. Straight lines need to be straight, diagonals need to be straight, transitions need to be clean and at the markers.
As for what the judge looks at in terms of the horse and rider combination, the biggest thing in the horse is a willingness to go forward from the aids, come back from the aids and submission to the aids in general - I guess you can group all of these points under submission. Going forward does NOT mean running flat out at a million miles an hour. It must be controlled forward, aka if you say jump, the horse says how high?. The paces must be free, balanced and maintaining a constant rhythm.
The rider must be balanced, have soft, quiet hands, a steady leg and strong position, with their aids quiet and effective.