The practitioners know what works in practice. They know the hundreds of little things that can’t be captured in a blueprint or a design. They know why one thing comes after or before another. They know why that seemingly dead space or irrelevant feature is actually meaningful. So ask them. Work with them to build whatever system or tool you’re creating. Sure, theory and higher level conceptual ideas are a key driver. But they pale in comparison to the needs and knowledge of those who do the thing. If you evaluate every input to the planning and decision making process and allocate a significance factor to it, mark input from the practitioners as one of the most salient.
I’ll give you an example. In hospitals here in the UK, it’s common for the higher ups to instigate the nationwide adoption of a certain treatment or test. When this happens, it’s common for the people performing the test that’s being replaced to say that the new way won’t work as well. A few years pass and, lo and behold, the new way is less effective than the old. But the people implementing these changes would’ve known that had they talked to people at the grassroots. In the example of hospitals, lives are on the line. One test instead of another can be the difference between detection of a cancer and death from it. So please, please, endeavour to ask the practitioners. Don’t build blind with faceless, supposedly-flawless statistics and conceptual models. Talk to humans as well.