How do you stay focused when studying? Tips?

Exercising definitely helps. There are hell lot of factors leading to poor concentration and lower motivation. But again, it is the person's responsibility to find out what motivates him and what bothers him. For example, in my case, when ever i focus too much on my studies, i neglect my exercise, which in turn leads to bigger waistline (something i hate). This bigger waistline along with other fitness issues lead to irritation, which inturn leads to a concern about my health and it then impacts not just my study but almost everything else too. So focusing too much on Gmat for days actually leads me to focus less on it for the days which follow.

Great question - I'm glad you asked this because I think a lot of people study ineffectively and that leads to burnout.

Many people study by thinking about duration (how long they'll study) or quantity (how many problems they'll do). But like with any workout program, if your goal is simply to cover the distance or put in the time, it can often seem monotonous or lethargic.

I'd suggest giving yourself specific goals or drills for at least 1/3 of your study sessions (if not more). Goals can include:

-Improving on timing by doing sets of 10 questions in 20 minutes
-Thinking about Data Sufficiency statements by looking only at 20 DS statements (and not full questions) and writing down what they tell you and what they need to be sufficient (so, doing a drill that's not just a pure GMAT question)
-Focusing on the conclusions of CR questions before answering them (again, more of a drill to emphasize important steps than just "doing questions")
-Noting one "trap" answer per problem in addition to simply answering it

By making these goals or giving yourself specific tasks, you can freshen up each study session while also focusing on important strategies and concepts. I liken this to doing drills or specifically-targeted workouts as an athlete - when I'm training for a marathon, some nights the last thing I want to do is "just run". But if I go to the track for a specific reason - trying to run a set of 400s or a set of hill repeats - the very fact that I'm focused on one specific goal keeps my mind fresher, and I still get the benefit of the overall mileage. The same can be true of GMAT prep - just "doing questions" can get pretty tedious, but if you have a unique purpose for that session you'll not only gain more in a targeted fashion but you'll also make the process of completing more questions that much more enjoyable and productive.