Just to re-iterate what Graeme says, the key is to eliminate refined salt from your diet, and replace it with unrefined mineral rich salt.
Refined salt is like the Hydra, its heads bob up everywhere. Even a sandwich from a supermarket apparently has 15 times more salt than a pack of crisps, or something like that. So you need to cut out all that junk.
The natural salt that De Langre espoused was Sel De Guerande. It is a grey salt from the beaches of Brittany. It is entirely harvested by hand, and has had no heat treatment. It is chock full of minerals, and apart from being very very good for you, is as Graeme says, wonderful tasting. Funnily enough I have an order just delivered from Village De France sitting downstairs on the kitchen table. I mention this because it is not particularly easy to source in the UK.
De Langre reckoned you could eat this salt in large quantities because it was so beneficial. In his opinion it literally washed the arteries.
I've been eating it for 3 months, and I eat it liberally.
The only drawback with this salt is this: the gulls fly over the salt flats where it is harvested, and their guana lands on it.
This affects it slightly, and causes a lot of flatulence when you take it!
The solution according to Dr Hulda Clark is to heat dry it at 205 degrees fahrenheit for 5 minutes in a pyrex dish.
I do not know to what extent this affects the salt.
Personally I don't do this. i use the sel de guerande for roasting, e.g. I laver over a chicken
and for sprinkling salt I use Himalayan Salt, (from Creative Nature) although there are many suppliers.
Other things you might consider for high blood pressure are : Hibiscus Tea (Cotswold Teas), Cacao Nibs (creative nature), and essential oils.
I use Ylang Ylang, and other oils,(contact me at above for more info)
Also as has been said, get the best water source you can.
Hulda Clark's first analysis of High Blood Pressure cases was water source. She reckoned cadmium etc in the piping was usually the cause.
Also eliminate caffeine in coffee and tea, and eliminate carbonated drinks.
also elimimate excess sugar. I.e. consume minimal amounts of sugar.
So as has been said, keep well hydrated with good quality water, and also study how to sleep well. Good sleep has universal health benefits, including blood pressure control.