I have used a mentor for my work since I first started photographing 6 years ago. His name is Scott Bourne . Over the years he has helped me by giving advice about both photography and business. At times I have paid for his expertise and other times he has offered free advice. It has been very helpful to me as I progress through my career.
Scott has posted an article that talks about Seeking Out the Advice of Others. I think you will find it very valuable as you look to improve your photography. I would highly suggest you find someone that is knowledgeable and very honest and unbiased about your work. Brutal honesty can be tough but very helpful as you critique your work.
Good luck and I hope you can find someone that can be as valuable to you as my mentor has been to me.