Here is an example of a letter that seeks to clarify a job offer before actually accepting it

Name
Street Address
City, State, Zip

Ms. Vera Argo
Recruitment Coordinator
Cargill, Inc.
Cedar Rapids, IA 52513

Dear Ms. Argo:

Thank you for your prompt telephone call concerning the status of my candidacy. I am very pleased to receive this employment offer for the position as a Quality Assurance Chemist, beginning at the end of May 20XX.

Before I make a decision about this opportunity, I would like to receive additional information about the position and about the orientation program for laboratory personnel.

I am very pleased with this opportunity to begin my professional career with Cargill, Inc. As you requested, I will make my decision before May X, 20XX.

I look forward to speaking with you in the near future.