the keyholes are my worst section, but generally my problem is that my mind assumes that they're drawn in perspective, when they're not. This creates some distortion in the angles and relative proportions in the object. Perspective, for those that don't know, is the illusionistic system represented by photographs that shows parallel lines converging to a point on the horizon. If you want to test this, just try to draw a cube on a sheet of paper from a slight angle. If you draw the lines at the back of the cube the same length as the ones at the front, it will look a little off (and be perspectively distorted). However if you let the lines that are further back in space be slightly smaller than those in front, you will create the illusion of distance and accurately portray the object (assuming you make those back lines smaller by the right proportion, which actually requires some slightly more involved techniques that are hard to describe in prose).
Anyway, the key is that they don't use perspective on the DAT, so the lines in the back of the object are the same length as those in the front, and the angles don't represent any perspective convergence. The problem with this is that even if you don't know what perspective is, everyone in the western world has lived their entire lives visualizing the world in perspective, whether they know it or not, so when you look at those images on the DAT your brain tends to interpret them with perspective in mind and thus interprets it wrong.
This being said, the ADA knows all this and instead uses different visual cues to let you see which one is correct. Therefore instead of looking at the overall proportions to chose your answer (which tends to be your first instinct) instead look at all the details, because its the details that will help you eliminate answers. By this I'm referring to the small bumps and crevices they put in the object, as well as using your marker as a measuring tool to see which sides of the object are of the same length (just hold it up to the screen and mark off the relative length of a side with your thumb, then compare it to another to establish a ratio like 1:2 or 2:3, then look for the same ratio in the answers, this is an old artist's trick). In the end you usually need to spend a full 15 minutes on this section, which means you have to make up the time from hole punching, angle ranking and cube counting to finish the test in time.
top/front/end is much easier, I miss maybe one out of 100 in these. again, the key to this is looking at details over proportion. The proportional issues are usually obvious (one twice as wide as another), so by looking for the same pattern of external and internal lines you can get your answer relatively quickly. My best piece of advice on this is therefore: <b> don't waste your time trying to visualize the object </b>. instead just compare the patterns of hard and dotted lines from one view to another. Unless you get two lines lined up on top of eachother, every line from one view will correlate to some sort of line in another view in the same place. For instance a hard line on the middle of the front view will always relate directly to a change in the outline contour from the left side of the end view (as its always pictured from the right). However there could also be a line on the right side of the end view in the same spot because when a dotted line and a hard line would be put in the same place, the dotted line disappears. typically though, you could then look at the top view to find common ground between these sorts of dilemmas.
Another problem people have with top/front/end is that circular forms tend to look rectangular in profile. Just think of a cylinder, like a soda can. from the top it makes a perfect circle, but from both the front and end views it is actually a rectangle. This is a very simple example, but on the dat they love to mess you up by showing a rectangular shaped cut out (dotted lines) from the front that in the end view is actually a semicircle. This is because you only get two hard lines out of the round part of the circular form- the top and bottom. As long as you remember to make sure that every line and contour from the two views given to you translate to some line or contour from the answer, you'll get it right. After all there is only one correct answer.
in case you're curious, I got a 24 on the real DAT, though that was on the low end for me. I usually don't miss more than 3 questions on the entire 90 question exam (uaually one or two keyholes and an angle ranking). Its all just about using all the information you're given and interpreting it correctly