Step 1: Mine Users Follows
Target users you are competing against, users in your industry, users you network with or wish to network with in the future, as well as significant users you respect that are in your niche within your industry.
Ex: @ChefBen Follows a number of chefs around the world. If you are targeting celebrity chefs, world class cities, cuisines, or unknown but prominent chefs, Chef Ben’s list of people he follows is a great resource
Step 2: Mine the User’s List(s)
An even more successful strategy for finding prospects is to check the lists that users (you trust) have created.
Ex: Again Chef Ben is a great example with his http://twitter.com/chefben/celebrity-chefs list. This list gave me a head start in building a planned prospect list I wish to follow on a controlled basis.