Economics is not a subject that is always straightforward. Many concepts are counter-intuitive and terms are often vague, if not cryptic. Go through your notes, skim over the chapters you've read and keep a list of the terms, topics, and concepts you struggle with. Most importantly, complete this step early on so you can get help and resolve confusion.
Nearly all economic concepts can be depicted with a graph. That is why your teacher will likely require you to identify and even reproduce some of the graphs related to key topics. This may not sound complicated, but it is easy to miss subtle details that will stand between you and the correct response. Make sure you can recall the labels on the X and Y axis, the units, the names of each line on the graph, where those lines intersect and what that intersection means in regards to economic theory. Also, know how those graphs change given different variables.
It may not be an essential exam tool for other subjects, but economics depends heavily on math and even more on graphing. It doesn't take many revisions to a graph with pen before the idea you are trying to articulate becomes confusing. Using a pencil saves you time and allows you to make revisions quickly.
Math is used in economics to verify the premise of a concept or idea. Often, students solve mathematical economic equations, but never check to see if the answer fits with the underlying principle behind the problem. For example, demand curves generally slope downward. If you calculate a demand curve that slopes upward, you should make sure you haven't overlooked an error in your calculations.