The things you should do to improve your reading depend a lot on your current level. You cannot makeover your reading skills overnight, but steady efforts can make a lot of difference! ETS actually has a quite comprehensive set of recommendations broken down by level, which are linked below.
|TOEFL Reading Skills
If you know roughly where you fall in this ETS chart, you should see their full set of recommendations! What follows below is a general set of recommendations to improve your reading skills. :)
Read as much as you can every day. Read a wide variety of types of texts, and write basic questions to test your understanding of a text. Test your knowledge of grammar to try to comprehend difficult sections of a passage, and stretch your grammar knowledge by reading slightly-too-hard texts.
Expand your vocabulary. Remember, the TOEFL tests your readiness for academic life, and it is important to increase your vocabulary on many subjects because you will have to read about various topics at the university.