Am wondering if people get there mares preg tested or do you let nature take its course?

I just let nature take it's course. By the time their nutrient requirements really start to increase, it's usually obvious that they are in foal.
On the odd occassion if there is one that I am really unsure about, like if I was pretty sure one was in foal but then the pregnancy seems to "disappear", I will use a weefoal test kit.

i normally let nature take its course with my experienced mares but with my maidens i always preg test i use the wee foal checker and have found them extremely accurate

I get our mares tested by our vet as it doesn't cost much more than the wee test and that way we can plan the year ahead with accuracy.

Does your vet scan/palpate or do blood tests, or both, or something else?

The vets at the clinic I use are very reluctant to scan/palpate Miniatures because they are too small to work inside of.

They scan. We have to wait a few months though to make sure something is visible since they can't check the whole way in being so small. When we first had it done I mentioned that to the vet and he said if they are too small to scan than they are too small to foal, which is something I hadn't thought of before but it makes perfect sense!