Freelancing: How do you specify your hourly rate for *new* clients?

For freelancers... Do you specify your hourly rate upon being asked (early on in process), or do you say you set a fixed budget (based on a proposal) for new clients?

I've read that specifying the hourly rate upfront can weed out deadbeats, and/or clients you don't want to work with, is this true?

Overall how do you, as freelancers, work through this process?

Thanks!