710 on first practice test, now what?

if you took this diagnostic cold [with no studying] then there is room to improve and actually get in to the 99 percentile. gmat is very learn-able and all you have to do is better you strategy and approach to each question type. on the other hand if you studied first and then took the test, you will still be able to improve your score but not as much as the preceding case i presented [this is just a probability].
one thing you should do is do enough questions that you can develop a pattern recognition understanding of questions while taking the test. this will only happen if you have done a lot of question types and familiar with every type of complexity that could be piled on a basic subject in each section.
to get into the deep 99 percentile you have to go beyond what typical gmat prep materials provide you, and master each subject and all the complexities it could present you. for example one method is to go through all the questions that you have done, despite you answered them correct or incorrect, figure why the correct answer is correct and why the incorrect answers are incorrect[this is very useful specially in the verbal section]. it is at this point that you will start to develop pattern recognition technique, and will kick some gmat ass...
more question you do and more accurate shortcut techniques you have developed to deal with each type of complexity that could be presented to you, the better you will do on the actual test...
the last part is the mental attitude. to score in deep 99 percentile you have to have the right mental attitude and toughness and never give up learning new techniques...

good luck to you and hope you do even better on your actual test