That is kind of the senior to help out, but it's good to first find out somehow if the knowledgeable person is the senior, or actually her parents. Also importantly, is the senior hooked in some way that made admission easier for him or her in a way that doesn't apply to your child.

As I wrote in another thread, the single most useful book I read re college admissions is Cal Newport's How to be a High School Superstar. We used that book's script with great success.

Re essays, take a look at Johns Hopkins "Essays that worked". One of my favorite ones is "Breaking into cars"