Network to find connections via your friends, clients and professional organizations. Constantly seek out new people with whom to connect and add to your circle.
Send publishers postcards or emails featuring your work. Address your postcards or emails to specific editors or art directors, and if you’ve met the person at a conference or other networking event, mention that meeting.
Create an online portfolio displaying work appropriate for book covers. Build a website, if you don’t already have one, so that editors and art directors can find you.
Submit to stock photography sites. Many art directors simply search for book cover images online via sites like Flickr or Getty.