620 is a good starting point. Scores are all over the map, but I'd say most people start in the 500s to 600s. I'll assume that you, like most students, want to score around 700, so you've got some work to do but you're at a good starting point to do so.
Re: quant vs. verbal, that is entirely individual - just depends what your strengths and weaknesses are!
Use this article to analyze your results and help you set priorities about what to study:
http://www.manhattangmat.com/blog/index ... ice-tests/If you're not taking a course, you may also want to read one of these two articles:
Just starting out:
http://www.manhattangmat.com/blog/index ... ould-i-do/Studying for a while:
http://www.manhattangmat.com/blog/index ... -the-gmat/