I'm sure this is a question that lots of people have even 7 years later.
The biggest room for improvement once you're scoring in the high 600's and low 700s is in your in-test process.
Anyone trying to move up from that score level needs to assess how well they're processing each question in both quant and verbal.
Ideally an expert coach -- with experience in in-test assessments -- can speed up and maximize that process. You can do it yourself but it's hard when you don't know what you're looking for.
I've worked with lots of people trying to make this exact jump (around 700 --> around 750) -- it's all about process. Forget going back to content -- it isn't going to create anywhere the same leverage and it takes way too long.