Tips:
The order and placement of pieces in a test is irrelevent.
Try to learn as much as possible in one test. Rather than testing a single red square, red circle, red triangle and so on for green and blue, test a red square (for red pieces and squares), a green triangle (for green pieces and triangles), and a blue circle (for blue pieces and circles).
If you vary two tests too greatly, you might not be able to figure out what made one test right and the other wrong.
Most rules are pretty straightforward, but some require very different thinking. For example "Exactly as many Circles as Shapes" will only be true for 1 circle of a given color and the rule may appear to be something like "Exactly 1 Circle" which isn't possible.

Example:

In the snapshot above, the player first tested the most basic components. All failed, so she tried several combinations to see how the pieces interacted. In the ninth test the rule appeared to be something like "more than 1 circle." The next few tests made it clear the circles had to be the same color. The player knew there needed to be 2 or 3 circles all of 1 color. How could the number of circles relate to the number of colors here? 2 or 3 is more (and not "at least as many") than 1. The player guessed "More Circles than Colors" and was correct. The player would (rightly) expect another test made with three circles of two colors to satisfy the rule as well.