Unfortunately there is nothing that one can do to prevent PE. It would be great if taking some vitamins, or eating certain foods could prevent it. Many people would be very happy. The one thing you can actually do is to make your life as comfortable and healthy as possible. Get a good OB, a good MFM (high-risk OB). Make sure your hospital is easy to reach, so you can go there on a whim in case you need to be seen quickly. I also found counseling helpful to get through a very scary pregnancy.
Your doctor should decide what is best for you in terms of supplements, but what seems to be the norm is LDA, Vit D, Calcium, prenatals. Some also need to inject blood thinners (lovenox/heparin), mostly due to a clotting disorder.
Higher dosages of Vit C and E is NOT recommended. It once was believed to be helpful, but it then turned out it did more harm than good and women got sicker quicker.
Here an old thread with similar questions (further down the thread blythe and caryn explain it very nicely)viewtopic.php?f=12&t=44240&p=346116&hilit=Vitamin+C#p346116
MC 3/2009 and 3/2011Henry
(1/1/2010-1/7/2010) - forever loved and missed; severe PE with Hellp; partial placental abruption, classical c-section at 25.6 weeksMatilda
(Nov. 2012, born at 35.4 weeks) - severe PE
Our pain has been put into words, placed into empty cradles, to remember that all our babies lived, that they mattered and always will. - Field of Cradles http://www.fieldofcradles.org/