Starting a new project, how do you even pick between microservices and a monolith? What's the best way to decide?

Okay, so we're starting a new project, and it's the usual monolith versus microservices discussion again. I'm thinking a monolith would be quicker to launch and easier to manage at first. But, I am worried about painful refactoring if we get really popular. What things do you look at when deciding this stuff early on? Are there any mix-and-match ways that give you the good parts of both without making things too complicated? I'd really like to hear about actual times where one worked out way better than the other, especially with certain team sizes or project needs.