I fold the paper in half diagonally to make a 45 degree angle. Then I use this to compare angles be putting it up to the screen.
The reason why this worked for me:
Lets say there are two angles that are 50 and 51 degrees. Having a 45 degree paper to compare will make it like comparing 5 and 6 degree angles instead, which would be easier to see than 50 and 51. Use the 90 degree edge for obtuse angles.
It is not a sure-fire method, but it does help a bit. Remember that on the PAT you dont have that much time, so this is just a quick tool that would only take a second to use, as opposed to writing on a piece of paper on the screen.