1) When my agent sold my first book to Five Star, she didn't make much of a commission, but she continued guiding my career , submitting proposals to other publishers, and giving me advice on how I could branch out into other genres.
2) My agent often contacted me when she was contacted by publishers in need of proposals. I spent the next two years writing a lot of proposals. I never turned her down, because I wanted her to know I was willing to work to "make it." Publishers contact agents when they need something fast, when they have a "slot" open up, or when they need a writer-for-hire. We received a lot of rejections, but my agent - - -
3) kept encouraging me! She still hadn't made any more money. My agent kept working with me, kept directing my career. It began to feel like she was a harder boss than my real boss, but I was learning to trust her.
4) My agent always returned my emails. I never called her, as I never had any urgent questions, but she always returned my emails promptly. She also sent me regular correspondence showing which publishers had rejected my manuscripts and proposals. We were/are a team!
5) My agent had her pulse on what was going on in the publishing houses. The last proposal she told me to write, I told her no. I was tired. I have a full time job, I was working on a sequel to THE COST OF LOVE, and I didn't want to do another proposal. She responded to my no, with an "I understand" email. This was quickly followed with a "let me tell you why you're wrong" email. I decided to follow her advice.
6) My agent was able to negotiate contracts for another 4 books with 2 publishers. She was able to negotiate the due dates on these books, and she was able to increase the number of free books I'd receive as well as a few other perks.
I'd say my agent is valuable to me. One of those 4 books we sold because the publisher had a "slot" open up and needed to fill it quickly. She went straight to my agent. Good writing can be noticed by a publisher without an agent, but you don't always know where those "open slots" are. Personally, I think an agent is worth her 15%. I know this isn't every one's experience, but it certainly has been mine. I hope if you have an agent now, or have one in the future, that it's your experience too.