What can I do to relieve and prevent sciatic pain in back and lower legs?

I am an avid soccer player and about 3 years ago started to feel sciatic pain starting on my lower back and radiating to my lower legs, specifically my left side. Ever since then it has been an on and off issue. For the past year or so I have felt no pain while playing or exercising, until the last two days, where the pain was just too much on both of my legs for me to even walk on the field. The only conclusion I can come to, is possible it could be that I am playing more frequently with less resting time, other than that I am not sure what could be causing it to come back to this degree. What can I do to prevent any future flare ups? Specific exercises, stretches, etc? or what has worked to "cure" you or others?