I was in this situation when I applied for grad school last year. I think it's easy to be complacent with average GRE scores and hope that other aspects of your application will shine through. Although it may not seem like it, it is very important to study for the GRE. In a way the GRE doesn't seem to test how smart you are, rather, it tests to see if you know all of it's tricks. Since the GRE only tests material that you would learn up until high school they are purposely try to trick you. In fact, they will do anything in their power to try and trick you and try to get you to answer in correctly. Put in the time and learn vocab and learn all of their tricks. The more you understand how the test writers are trying to trick you. The better you will do. I took the GRE last year and this year. Last year I didn't put the time into studying and it showed. This year I took it much more seriously
2014 Verbal: 153 (59 percentile)
2014 Quantitative: 156 (64 percentile)
2014 Writing:4.0 (56 percentile)
2015 Verbal: 157 (74 percentile)
2015 Quantitative: 161 (80 percentile)
2015 Writing: 5.0 (93 percentile)