Okay, there are a lot of different boots out there, so the first thing I have to tell you is go try some on. They all fit different, they all feel different. If you live near one, go to a scheels, especially if you live near a big one. They will take care of you and I promise they will have a great selection. Otherwise try an outdoor specialty store, NOT ONLINE.
Depending on what you are doing there are different shoes. If you are doing trails with no pack or a very light day pack, use a light hiker. You can even use a heavier trail runner. I would suggest looking at salomon XA Pro 3D or Keen wasatch Crest. These are trail runners. Or for light hikers try the Merrell Radius or Outland, or the Keen Voyaguer.
If you are getting a little more agressive or wearing a heavier pack then you should get a light hiker in a mid. I suggest the Merrell Radius mid or outland mid, or the Keen Targhee Mid
Finally if you are backpacking. I would suggest the Vasque Breeze mid or any Asolo. Backpackers all have shanks so they should be pretty good for the pronation issue.
Again, try them on, try them on, and try them on. That is the only way to tell. The shoes I recomended are all good for flat feet, and should do you well. I can't over recomend Keen or Merrell. They are great shoes. Hope it helps
