How do I sign a business letter with the company name in it?

Question

Bla Bla, Vice President
National Junior Honor Society

Like that? And would the title (vice president) be behind or in front of the name?

Yeah, but I want the National Junior Honor Society to be part of the thank you (it's a thank you letter), not just to indicate that I'm the vice president of it.

Answer 1

Just the way you've written it:

Yours sincerely,

(Signature)
Bla Bla OMG, Smileys!!!,
Vice President,
National Junior Honor Society

You're signing in your personal name, so it's yours sincerely. If you're signing the name of a firm, then it's yours truly.

Answer 2

Exactly like that. Or the title can be listed below the name and above the company... either way is acceptable.