How should one write the peer recommendation?

I’m applying early decision to Dartmouth need help regarding the peer recommendation. I have a friend with good writing skills willing to write it for me, the only problem is that neither of us know what a recommendation letter actually looks like.

How should it be opened? Would it be like: “I am XYZ, a friend of ABC and am writing this to recommend ABC to Dartmouth College”? How should my friend introduce himself in the letter?

How formal should the language be? What are we actually supposed to write about? How long should the letter be?
Any guidance is appreciated.

From what I’ve heard about the peer letter, it should definitely be a bit informal. Yes, it’s a recommendation, but the acceptance board is trying to see a different side of you that they otherwise would not have seen in a teacher rec. Obviously, don’t be flagrantly informal but being a tad more colloquial is advised.

“The first time I met XYZ …”
“XYZ hit me with a water balloon when we were 3 years old.”
“I was about to hit by a police baton during a protest about … when XYZ”

It’s not a formal letter of recommendation. The person should write what s/he feels and knows about you.