Practice doing addition, subtraction, multiplication and division quickly in your head. About 1/3 of the math questions on the PCAT require you to simplify numerical expressions or solve simple word problems involving proportions. You won't have time to work out all of these problems slowly on paper. The more you can do in your head, the better you quantitative score will be.
Review basic concepts of pre-calculus, focusing on functions. What is the limit behavior of a polynomial, exponential or rational function? What do graphs of these functions look like? Review polynomial factoring as well.
Review basic single-variable calculus, focusing on derivatives and integrals. Polynomials, exponential functions, and rational functions will be tested on PCAT calculus.
Don't worry about geometry, as this will not be tested. You may see a few questions that test your knowledge of sine, cosine and tangent as functions.
Learn to spot wrong answers at a glance. Each PCAT math question only has four choices, so if two or three) look wrong to you automatically, you'll be in good shape.