How do I maximize the value of each GRE practice question? (redo it multiple ways)

Don't just check whether you got it right or wrong. For every question worth studying, try solving it multiple different ways and figure out which method is fastest and most accurate for you. The goal is not to get through more problems but to extract maximum insight from each one so that when you see a similar question on the real test, you use the approach you've already determined is best.