To increase your Quant you need to master the knowledge contained on the GMAT, there is only a finite number of topics that are tested on the exam and you need to know each of those topics in detail. You should be able to identify the concept(s) of a problem within the first few seconds. Then you need to focus on how to test within those topics - there techniques that can help you through some trouble spots or help you with time management. The key to improving on quant is to make sure that you learn something from each problem that you do - simply doing problems to see if you get them right is not always beneficial.

You should also be taking pretty consistent diagnostics - make sure that what you are doing in a study session is actually translating to increases on the actual test.

There are lots of study plans on this website to use if you are planning to self study. If you find you don't have the discipline to consistently study every day then you may consider signing up for a class or hiring a tutor who can focus on both technique and math knowledge.

Best of Luck