Know the equations. Calculations on the MCAT are not hard, but if you don't know the formula, then you can't even do the easy calculation. In fact, many answer choices are as simple as "doubles", "triples," "stays the same," "decreases by half" or "decreases by a third." The key is to know the formula.
Associate MCAT Physical Sciences passages with large key concepts, such as acid-base chemistry or batteries. Being able to recall the major pertinent formulas by just thinking of a concept will save you a lot of time and earn you points.
Know certain key concepts very well. The MCAT is famous for thermodynamics and kinetics questions. You can guarantee that there will be some delta G questions to answer. Acid-base chemistry is also a very popular topic. With only a handful of passages and several questions for each passage, it really pays to know these concepts.
Know your inorganic chemistry trends. It is easy to get turned around thinking about stoichiometry, electronegativity, atom radius and more. These topics should be easy, but they trip students up during a high stakes, timed exam.
Walk into the exam knowing general electricity and magnetism trends. The MCAT Physical Sciences section is only 52 questions long as of the publication of this article. With about half going toward general chemistry and half going to physics, you're only left with roughly 26 physics questions. Within physics, probably only half of those will deal with second semester physics -- i.e., electricity and magnetism. You do not need to master all the fine details. Remember that the MCAT is about testing reasoning skills by applying concepts to situations that you haven't seen before.
Take practice tests. You can find MCAT practice tests online. Practicing will help you become familiar with the types of questions you'll face on the actual exam.