Here's what I do.
1. I never trust those machines.
2. I always take my blood pressure at home after I've been sitting for at least 15 min.
3. I take it at a variety of times. Sometimes first thing in the morning, sometimes at work and sometimes in the evening. I never panic unless I get 3 consecutive high readings - which has not happened for years.
4. I do watch carefully what I eat now and always read the labels of what I buy. Where possible, I purchase low salt foods. Canned tomatoes and bottled spaghetti sauce are two things I don't buy anymore just to name a couple. Too much hidden salt.
5. I have also cut back on dairy. I cut out the milk and only drink soy milk now. I've cut way back on cheese (that was the hardest thing to do) and eggs too.
6. I only eat meat 3-4 times a month. My protein mainly comes from beans, legumes, tofu and fish.

I'm on two different blood pressure meds along with a water pill. The meds along with my modified lifestyle are doing the trick for me. Oh yes, and there really is something called the whitecoat syndrome - even my GP admits it. My BP is always higher in the doctor's office, but she's happy as long as it's normal at home.