The GRE Verbal section aims to determine your grasp of the English language. If you are a regular reader of novels you should have no problems with the passages. If you are not, well, its never too late to start. Sit with a dictionary and read the editorials of leading newspapers regularly. Editorials are about the same size as a GRE passage. They are sometimes tough to comprehend and they are full of "words". They sometimes cover socio-economic issues and you must read these even if they dont interest you, as they will train you to concentrate on boring passages. Leading dailies also have Science passages. Try to understand these passages and you will be able attempt any question that a scientific passage in the GRE throws at you.
Even veteran readers may not be used to reading long passages off the computer screen. It may cause a strain on your eyes. Its advisable to get used to this strain. Hence if you have access to a computer, logon to the sites of leading dailies to read the editorials.
The regular reading of newspaper editorials will not only enrich your vocabulary but will also increase your general awareness of the world around you, giving you an insight into current socio/economic/political issues and keeping you abreast of your colleagues.