First line: Dear Sir or Madam / Dear (name)

Friendly open: It was a great pleasure to meet you in....

Previous contact: Thank you very much for sending.../ Further to our earlier conversation....

Reason for writing: I'm writing with regard to... / I'm writing to find out more information about...

Request: I was wondering if you could..../ I would be grateful if you could...

Offer help: Would you like me to...? / If you wish, I would be happy to...

Final comments: If I can offer any further assistance, please don't hesitate to contact me. / Please feel free to contact me if you have any questions. 

Friendly close: I look forward to hearing from you. / Give my regards to....

Last line: Yours sincerely / Kind regards / Best wishes