Create your own following, especially online. If you have social media channels full of followers, a large email list or a website that gets a great deal of traffic, a publicist will see potential in your built-in audience and be more interested in working with you.
Create a catalogue of work. This is especially valuable if you're looking for a publicist before you begin a shoot, as your past work will serve as a kind of calling card.
Talk to other filmmakers who are more advanced in their careers about publicists that they have used. The truth is that anyone can claim to be a film publicist. Referrals will help you to find hardworking, legitimate publicists that have produced real results.
Contact publicists in your area. Create a list based on the referrals you gathered. If you need more resources, contact film schools in your area. They often have resources that include contact information for local industry professionals.
Interview potential publicists. The pairing of a publicist and a film requires agreement on both sides to partner on the project. Choose a publicist who has references as well as a solid track record and a detailed plan for publicizing your film.