Formal letter writing

[ThisistheHenry]

I am in the process of writing a thank-you email to a Japanese professor, and I was just wondering if there is any format that is generally followed when writing such.
Should I start with 成田先生へ? Is there something more formal?
Are there words that I should use to start/end the letter?
I'm not asking nor wanting for the letter to be written for me, but I would greatly appreciate some pointers as far as formalities in emails go... since I don't want to mess this up
宜しくお願いします

[jkid]

I can't comment specifically on format because I am not confident enough that I will give you the right information but the page here: http://japanese.about.com/library/weekly/aa101401a.htm may provide some help, I'm not sure of the level of formality though.