I'm trying to think of something that I blindly follow, but I can't.
There's always some reason behind it. If my mechanic tells me my transmission's bad I take his word for it. Why? Because he's qualified and I've dealt with him in the past. And before I ever dealt with him, someone I trusted (for good reason) recommended him. And, if I really felt like it, I could learn enough about my car's transmission to see for myself.
