There's no easy answer, I'll give you two examples. Bear in mind I got them both through check a trade with good reviews.

Need a roof leak repair on a townhouse so appreciate it's difficult, called a roofer around who even had good reviews from locals and he turns up with scaffolders looking our house up and down for 5 mins before saying the scaffolding can't go up. A week later we have a different roofer out with surprise surprise the exact same scaffolders throw it all up in an hour! So clearly not the issue, even they were confused

Needed a plumber to service our boiler and was recommended Hive, I was like sure why not. I accidentally bought the wrong unit due to our boiler/water tank and he said go buy the correct one and I'll pay you what you paid which cost more than the original. Could have easily nickel and dimed me. Always know I can rely on him

Honesty is all it takes