Triangulate
Come at it three ways that share no source; keep only what all three agree on.
What people do, what they say, what the record shows — where all three agree.
Seen in Forensic Architecture (Forensic Oceanography), The Left-to-Die Boat, 2012
Try it on your work
Establish one fact about your situation three independent ways: measure it, observe it in use, and ask someone, without letting any method see the others' answers. Agreement is confidence; disagreement is a finding.
Ask three people who don't talk to each other the same one question about your project. Where the answers converge, believe it; where they scatter, the question was really three questions.
Estimate one quantity by three unrelated routes: top-down, bottom-up, and by analogy. If the three numbers disagree by more than double, the quantity isn't what needs attention; the model is.
How it has been used
Come at one point from three independent directions: the surveyor's method, the journalist's three sources, the same question asked of the maker, the user and the material. The move forces independence: if two of your three positions share a source, you have two, not three.
Where it leads
Grouped under Help the parts agree