It is very difficult to get an agent, I fear. Writer's Market is probably the best location as far as I know and I haven't looked at one for years. It is a sizeable book with lots of good advice and more importantly actual names and addresses. It is published annually. Make sure you are using the most current edition. It would be available at your local library. I managed a B. Dalton Bookseller, so I was selling them not using them.
Best wishes to your friend and tell him/her not to get discouraged if he/she needs to contact a lot or as I'm informed-- hundreds of them. I read on Jim Butcher's Journal site that he realized he didn't have to be the best writer in the race, he just needed to last longer than the person next to him. Or something similar; it isn't an exact quote! Seems like good advice to me!
Meg in IA