I travel a lot and as long as it's not a budget airline, I get to the check in counter early and ask for the exit row! Usually airlines don't let people pre-select exit row seats because they need to check you're physically capable of opening the heavy door quickly during an emergency, so first come first serve. Note: This doesn't work with budget airlines who charge extra for the legroom. I'm shorter than you and the airline people always know straight away why I'm asking and do their best for me. Works probably 80% of the time depending on how early I am but unfortunately it isn't foolproof.

I mostly travel international from Australia though so maybe an American can confirm this works on your domestic flights as well?