I've been seeing nephrologists (some of the best in the country) for almost a decade, and none of them has ever been remotely useful in planning out a diet. Neither have the nutritionists they've sent me to. They all know lots about nutrition, but they don't know anything about food. They also get really cagey/evasive when you try to ask for quantifiable guidelines -- like "tell me how many milligrams of potassium to stay under per day".
And don't get me started on hospital food. (Short version: my "renal diet" at Cedars Sinai was just half-portions of the regular diet -- including half a banana, and a 4-oz container of orange juice. No joke.)
Watching serving sizes is the trick, because "suggested" serving sizes are usually totally unrealistic. People will tell you to avoid spinach like the plague because they're used to thinking of it as a crapton of leaves boiled down to a few spoonfuls. But they might make you so paranoid that you avoid a sandwich that has three leaves of fresh spinach on it, despite the fact that there's more potassium in the bread! And conversely, they might not mention potatoes, because the suggested serving size is so small, but you'll get a ton of potassium if you eat a giant plate of french fries (potato skins even more so).
Some things nobody told me:
1) A baked potato has twice as much potassium as a banana.
2) So does an avocado.
3) Some fancy grains, like quinoa, are reasonably high in potassium.
4) Foods claiming to be "a good source of potassium" aren't always the most potassium-rich; that's just marketing, and tells you more about the calories per unit potassium than it does about the potassium per serving.
Often what is used to 'replace' salt is potassium chloride, which would be dangerous for those with kidney issues. I take a popular medication for high blood pressure control, lisinopril, which can interfere with potassium elimination by the kidneys so I have to be careful with it myself. I haven't needed to avoid potassium-rich foods which contain it naturally (periodic testing of potassium serum levels confirms this), but artificial supplementation with potassium chloride can be especially dangerous; V-8 vegetable juice is an excellent example: it's processed so heavily during production that nutrient are destroyed, so supplements are added, including enough potassium chloride to bring potassium levels to > 700mg in a 6 oz serving, so it's best avoided.
Ironically when I aske about the lo-salt versions of things like soy sauce she commented no the crap they put in to replace salt is worse :-)