The first step to increasing your GRE score is to understand the scoring system adopted by the GRE. There are a variety of wrong ideas about how this happens when it really is a simple system to understand.
The GRE is a Computer Adaptive Test or CAT!
So what if it is computer adaptive you may ask. Well, this makes all the difference. In the CAT version of the GRE, the saying "first impression makes the best impression" really holds true. This is because in any computer based test which "adapts", the main objective of the computer is to increase the level of difficulty of the questions until it reaches a level which you find challenging.
So what does this mean for you?
This means that you will only have one attempt to answer a question and then you move on. Unlike a paper based test where you can recheck your answers, in the CAT system your response on the current question will be used to determine the difficulty level of the next and so there is no chance for you to go back and correct your answers. This means you should take utmost care while marking the first few questions.
Let me explain more in depth:
In general the first question in any section is one of medium difficulty. By "medium difficulty" I mean that of any 100 people who attempt this question, fifty would get it right and the other fifty would typically get it wrong.
This means that you will be able to move on to a higher performance level if you get the first question right. In the GRE each question comes from a database of questions. The questions in this database are categorized depending on the percentage of people who get them right on first try. Marks allotment for getting each question right is also predecided by the computer based on the difficulty level of the particular question. If the question you get is considered to be hard then you will be given more marks for getting it right than for getting an easier question right. What this means is that a person who gets his first few questions wrong and then get many questions right (since the difficulty level and hence the marks decrease once you make an initial mistake.) will score much lesser than the person who has answered the first ten odd questions right and then makes a silly mistake. If he has performed well on the first ten to fifteen questions then if he makes a mistake later on the computer will be more forgiving on him and assume that he has made a silly mistake and thus reduce lesser marks for a wrong answer.
This type of question pattern can be plotted on a graph where the curve of the graph needs to be increased from the beginning itself. If this is not done then even if all the remaining questions are answered perfectly you will not be able to score in the high 700's.
Practice is key to making sure you get the first few questions right. Your time management will be tested here since you will have to ensure the correctness of the answers right in the beginning and you shouldn't mess it up. As mentioned earlier I used the Barron's math review chapter to make sure I was up to date with the concepts tested. I found it to be more than enough for my preparation. You will find all the concepts tested in the exam explained in simple language with many sample questions to practice these concepts on.
Making the effort to understand the GRE scoring system perfectly will ensure that you will be able to manipulate it to your advantage and be well on your way to a perfect score.