Which research methods have helped you curate your buyer persona?

I think a lot of people talked enought about tricks and tips to get “better”, so I’ll instead will talk about the failed experience and mistakes that I made during the first’s try of collecting information.And, all that happend before I knew Hubspot.
The main mistake was the over focus on gather to much “sample”, I spend a lot of time to just collect hundred and hundred of contacts ,and even more time on building the sheet with all the information my team had at time.At end I couldn’t make even a standard and efficient questionaire to use on these prospects, I had to improvise a lot of question base on their individual caratheristics, and improvising usually means also “unprepared for the unexpected”, which caused a unprofessional image of myself and my company.
If before to start blindly the action, I would engage a meeting first, with all the member of the team, discussing and filtering the buyer persona, we can get more specificic sequences and actions.That could lead to something better, I believe.