GMAT Quant Preparation: Different Strategies

Quant Section:

The 37 questions in this section comprise two kinds of questions:
Problem Solving (PS) and Data Sufficiency (DS). The two kinds do not have a definite break-up, usually there are around 20 PS and 17 DS questions. The level of Math-skills required is of High-school level. All the stuff tested here is on "the basics". One should be thorough in basic formulae and concepts to crack this section.

DS-Strategy:
DS Problem is a bit difficult in the sense that it requires a bit more time to solve when compared to a PS problem. It requires a careful approach which deals a step by step elimination of the options. If one does not follow the process, there is a high chance of landing on a wrong choice. Weigh the two given statements independently to decide whether either one alone is enough to answer. If both the statements are not independently enough to solve the problem, then check whether both the statements together can do. Go through this link for more light on DS strategies.
Silly Mistakes:

Don't be too fast while solving the problems. Even if you are strong in Quant section, go with a balanced approach. Be careful with the traps. More balance is required especially in dealing with DS problems as we are more prone to traps there.

Prep-stuff:

After completing OG material, try out some advanced books like "Manhattan Advanced Quant Book" to get more varieties of flavour. Go through the challenge Q's, 700-800 level Q's on prominent sites and stuff. 

Time-Strategy:

Time would not be a big constraint while solving the 'Quantitative' section, provided enough practice is made judiciously.

For Quantitative section, the given 75 minutes of time to solve 37 Q's leaves us a solid 2 minutes (or 120 seconds) time for each Q' on average. But as an average-PS problem generally takes lesser time than that of an average-DS one does, there should not be any strict emphasis on limiting each problem to 2 minutes. One problem may take 150 seconds while the other may take 90 seconds only. Some lighter ones can be cracked even in less than a minute's time. So instead of keeping track on time taken for each problem, it is better to have an overall track on a bunch of problems (say 5 or 10 at a time). Timed Practice with keeping these things in mind builds one's confidence in tackling any issues with time.

Best method of calculation:

"Calculations performed in mind save a lot of time when compared to calculations put on paper".

"Performing calculations in mind" can be built by developing liking towards numbers and practising a variety of exercises on a regular basis in study and non-study hours. Whenever we come across a number, trying to find out its factors, trying for divisibility tests on it, checking whether it is a prime or not etc. in mind automatically make us develope a liking towards calculations and shed off fear of math.