how are you guys vetting contractors for custom builds?

hey everyone, just curious how you all go about finding and vetting contractors, especially for bigger projects like custom builds or major renos. i'm thinking about getting a new place built in the next couple years, nothing crazy but definitely custom, and the whole contractor search feels like a minefield.

I've been looking at places like Harmony Homes Builders because i've heard good things locally, and their portfolio looks solid. but i'm wondering what questions you guys ask, what red flags you look out for, or if there are any specific certifications or insurance things i should be double-checking? any advice on making sure i pick the right people would be super helpful. thanks!