List them too. You see the pattern here. Centers of influence are basically people who liked your work or who like you. They might be willing to make calls on your behalf or maybe just take your call. They are invaluable in this career.
Many actors use the shotgun method.
I recommend the rifle approach. Research the productions and find out who is using actors of your type and demeanor. Then find out who the casting director, producer and directors are and make a list. This is where you should focus your energy. Watch the credits, use our database, go to the library, use the IMDB or any of a hundred other ways.