Join a guild, club or association. This is the first place where you'll find others with similar agendas to yours. This is the best place to find out what's new and inspiring with your craft. Find new clients. Word of mouth travels faster when it's good words than any ad can.
Referral work is always the best.
You feel great when someone who admires your art refers another person to you. Keep in touch with current and past clients. Again, this cannot be said enough. It is those clients who purchased from you first. They took a chance on your work.