First step ...
Check my
5-Minute Lessons and read the article entitled
Promoting yourself and/or your band.
You could hire someone ... but they would just do what you can do yourself. The real advantage I see in hiring a publicist is that they can focus all their energy and attention on promoting you. If you hire a seasoned publicist ... you'll be taking advantage of all their contacts and business relationships, which is what the music industry is all about ... relationships.
You might want to pick-up a copy of this book ...
All You Need to Know About the Music Business