I tried first the hitting-a-stop method. This worked but eventually the fine pointer I was using (as an indicator rotated by the stepper) broke off, likely due to the repeated impact with the hard stop.
I replaced the needle with a more robust one but found that the added mass hitting the hard stop made it very difficult to get repeatable stops.
So I replaced the hard stop with a limit switch. I think the limit switch is a much better choice, especially if you need to precisely locate the rotary position.
BTW, I never mentioned my project. I've built an accurate outdoor thermometer and use the Arduino to drive an analog temperature gauge. The sensor (AD590) is inside a triple radiation shield with forced air ventilation.