How did you build your waitlist?

My co-founder and I are building a tool to automate prospect research for salespeople, and we opened our waitlist a few days ago. So now we're wondering, how do we actually get people to sign up?

How did you build your waitlist when you launched? What worked well and what didn't? And was the thing you did that got you the most signups? Would love to hear your stories. Thanks in advance!