How do you validate your product idea before building/creating it?

Hey! How do you do market research and product idea validation?
In other words, what is your flow to validate your idea if you want to proceed with building the product? I don't need details (but would be appreciated :D), just what is your flow to set the product up for success before you start building yet (eg what tools you use, what you focus on, what you look at first etc) Thanks a lot in advance