Open a spreadsheet and write down what you think are your ideal customers / users. You don’t need to read a book on the theory of persona building. Just try to define as much as possible who you think your ideal buyers & users are.
Set a number of interviews / meetings that you want to conduct weekly. Ex: We want to interview 5 people per week (who match your personas defined at step 1).
Conduct these interviews like open discussions. Don’t try to sell your product. Don’t feel the pressure of being a sales. Just discuss with them about their problems, their habits, the tools they use etc… and if the flow is right then talk about your product.
Distribute this task to 2-3 people in the team. CEO has to do it, ideally with the product guy and the first “all around” marketing person. Ex: two itws per week for the CEO, and one for the product and marketing person.
Take notes for each interview and share them with the two other people doing the interviews. Write a weekly (or monthly) report summing up the main learnings that you share with the whole team.
BTW I, by no mean, pretend it’s easy. Being consistent and interviewing users is hard.