How do you identify user needs and attitudes for a product you want to build?

For this we do write Personas as well as "Jobs to be done". When you use both approaches it makes things more clear, you get to right direction with a little extra effort. We do a lot of research and try to gather as much information as can, so that we don't miss a single bit. Then we sit over this and share our feedbacks and brainstorm and propose different ideas/solutions. After that we vote and make a decision what to do next.