Best Answer - Chosen by the Asker
What is the reason you're contacting him? The tone of your response varies depending on why you're contacting him.
For instance if it was regarding a job it would be formal:
Dear <name>,
My name is <your name>, <your friend's name> passed on your email to me as I'm extremely interested in the <name of job>.
Yours sincerely (if you know the name of the person who you are emailing),
<your name>
If it was more friendly however, i.e. you want to join his amateur hockey club:
Hi,
<friend's name> gave me your email, I was wondering if I could get some more information about the hockey club, I'm interested in joining ~~~ [be aware that this is not all grammatically correct, as to sound more colloquial and friendly grammar often gets less strict]
Cheers! (or thanks a lot)
<your name>
Hope that helps.
