Your first stop is here: http://www.ets.org/toefl Or, you can search for "improve toefl score". There is A LOT of information out there. A score of 90 is a pretty low goal. In some cases, it's not enough to be useful. Why not set your goal higher? My own tip: don't allow yourself to make basic mistakes. I've corrected your question so you can see your errors. "How can I get a TOEFL score of 90?"