What is the best way to study for the GRE?

Follow the study cycle: learn content, practice problems, take a full practice test every two to three weeks, review that test in depth, and adjust your focus based on what the review tells you. The review step is where most of the real learning happens.

Daily consistency matters more than marathon sessions. Even 30 to 60 minutes every day is better than sporadic four-hour blocks. Use different-sized study blocks for different purposes: shorter blocks for focused problem sets and vocab, longer blocks for practice exams and deep review. Vocab in particular is ideal for squeezing into spare moments throughout the day.

The more constrained you are on time, the more important it is that every hour counts. Doing the wrong thing won't get you there no matter how many hours you put in. If you're not making the progress you want, the fix is usually to change what you're doing, not just to do more of it.