I have been a GMAT tutor for a while now and have recently compiled all my knowledge and advice into a GMAT study guide that I am selling on my website. This is such a great community for GMAT prep, that I wanted to offer you all a discount. If you use the code: "mba15" you can get my book for $14 instead of the full price $29.
The book includes lots of advice on how to study efficiently and effectively, so you don't waste any time on poor study habits. It also explains they key tips to mastering each question type.
Check it out here: GMAT Study Guide