Hi SusieShushi,
Since your GRE quant score has plateaued, it’s a likely sign that you have numerous weak areas in quant that must be addressed. In order to find and then strengthen those weak areas, you should follow a linear and structured study plan that allows you to learn each GRE quant topic individually and then practice each topic until you’ve gained mastery. Let me expand on this idea further.
For example, let’s say you are learning about Number Properties. When learning about Number Properties, first spend time learning about the various topics within Number Properties, such as LCM, GCF, units digit patterns, divisibility, remainders, etc. Once you have developed conceptual knowledge, practice what you have learned by answering 50 or more questions just from Number Properties. When you do dozens of questions of the same type one after the other, you learn just what it takes to get questions of that type correct consistently. If you aren't getting close to 90 percent of questions of a certain type correct, go back and seek to better understand how that type of question works, and then do more questions of that type until you get to around at least 90 percent accuracy in your training. If you get 100 percent of some sets correct, even better. Number Properties is just one example; follow this process for all quant topics.
When you are working on learning to answer questions of a particular type, start off taking your time, and then seek to speed up as you get more comfortable answering questions of that type. As you practice, do a thorough analysis of each question that you don't get right. If you get a remainder question wrong, ask yourself why. Did you make a careless mistake? Did you not properly apply the remainder formula? Was there a concept you did not understand in the question? By carefully analyzing your mistakes, you will be able to efficiently fix your weaknesses and in turn improve your GRE quant skills.
Each time you strengthen your understanding of a topic and your skill in answering questions of a particular type, you increase your odds of hitting your score goal. You know that there are types of questions that you are happy to see and types that you would rather not see, and types of questions that you take a long time to answer correctly. Learn to more effectively answer the types of questions that you would rather not see, and make them into your favorite types. Learn to correctly answer in 1 minute and 45 seconds or less questions that you currently take five minutes to answer. By finding, say, a dozen weaker quant areas and turning them into strong areas, you will make great progress toward hitting your quant score goal. If a dozen areas turn out not to be enough, strengthen some more areas.
So, work on accuracy and generally finding correct answers, work on specific weaker areas one by one to make them strong areas, and when you take a practice GRE or the real thing, take all the time per question available to do your absolute best to get right answers consistently. The GRE is essentially a game of seeing how many right answers you can get in the time allotted. Approach the test with that conception in mind, and focus intently on the question in front of you with one goal in mind: getting a CORRECT answer.
You also may find it helpful to read this article about
How to Increase Your GRE Quant Score