Read about the admission requirements for the graduate programs you are considering applying for. Some will require the GRE General Test. Others will require GRE Subject Tests. Some programs will require no test at all. If the GRE is optional for your program, weigh your options. If your undergraduate grades were low and you are confident that your GRE scores will show your true ability, take it.
Register for the test. You can find out where and when the test is offered and whether that location offers the paper-based or computer-based test. You can even register to take the test through the website. When doing this, consider when you want to take the test. It is important to leave enough time to study, but also pay attention to deadlines for applications at the schools you are interested in.
Familiarize yourself with the format of the test and test questions. The GRE website is a good resource for this. Through the website, you can read about the test as well as reading sample questions. Being familiar with what the test will be like will make you a lot more confident, which can help you perform better.
Plan your study sessions. Once you've read about the test, you will want to study for the test. Study all the test subjects but pay particular attention to areas in which you believe you are weak.
Take the test. Go into it confidently. Monitor your time and make sure to get through all the questions.
Wait for your scores. If you take the GRE General Test on a computer, you will get your qualitative and quantitative scores immediately. Your writing score will take a few weeks. If you take the paper exam, you will need to wait a few weeks for all of your scores.