I'm battling this, too, and I'm getting my BP to reduce, just by doing these things:
1) Seriously, it is physically imperative to try to avoid stress. This means I have delegated more of the day-to-day 'fights' to my DH (like when the oil man over-charged us or the repairman broke my drier.) I've also skipped a few meetings at work, if I could, and started working from home 1 or 2 days a week, if possible.
2) Try to lie down on my left side, quietly, at least 20 mins at least 3x/day. (My m/w recommended 4x/day, but I just can't seem to find that time or remember.) Usually I do it 1 or 2 x/day
3) Take a good calcium+magnesium supplement just before bed. My m/w said your body absorbs it better at night when you are not drinking or eating anything else.
4)SWIM, SWIM, SWIM! Just being in the water helps, but swimming/exercising in the water is supposed to really help. The weight off of my back and knees feels good, too.
5)Yoga/meditation at night after work, as often as I can. I usually get to this about 4x/week
6) Of course, reduce salt, which also means reduce pre-made/store-made foods, fast foods, foods that come from a package or can, fried food, cured meats...
7) Drink LOTS of water - more than you think you can. When we drink LOTS of water, it helps reduce water retention and bloating, which, in turn, is related to our BP.
8) Exercise daily is very important. Just a 20 min walk a day is enough to help if you are not already doing this. I'm now either walking or doing a short pilates DVD in the morning, and swimming or doing yoga in the evening. I miss a lot of 'sessions', both morning and night, but it is more than before!
Good luck! I'm only 21w and struggling w/it already. I'm terrified of being induced and not having the waterbirth that I want for me and my baby. (FWIW, this has also slowed down my weight gain, which I'm sure is helping the BP, too.)