Two things I do that help when the pain hits (before I can get to a chiro):
--Sit on an exercise/birth ball and roll back as far as I can (so I'm doubled up on myself with my rear going toward the floor) to really stretch the hip muscles. I'll angle myself to stretch one hip and then the other. Of course, I have to hold onto something while I do this, or I'd fall right over.
Also, just sitting on the ball and moving my hips around in circles helps a lot. And I try other exercises on and off the ball that stretch the hip muscle and the thigh muscle.
--I lie on my side and have DH take his elbow and press it down really hard right on the most painful spot on my hip. Yes, it HURTS, but it hurts in a good way, and it helps calm down the spasming muscle. Sometimes I'll have him do this in the middle of the night if my hip is bothering me so much I can't sleep. My mom has sciatic pain sometimes, and her bed frame is right at the same level as her hip, so she'll lean into the sharp corner of it to put pressure on the spot in the same way. Maybe a kitchen counter or dining room table might be the right height for you?
And things I've learned to help avoid sciatic pain:
--Don't cross my legs at the thighs/knees (the lady-like way).
--Keep my body as symmetrical as possible. That is, don't sit on one leg, don't sit on the floor leaning on one hip. I try to keep my legs/knees/hips parallel.
--Don't sit for long periods, especially at the computer where I'm most prone to have bad posture.