A personal opening, a one- or two-sentence mission story, a specific ask, what the business gets in return, an easy way to say yes and a clear deadline. Have your EIN and 501(c)(3) status ready for corporate requests.
Both work best together. A printed letter carries weight as the formal ask, and a short email is faster to send and easier to follow up on.
Send a short, friendly nudge about a week later. Acknowledge that things get busy, restate your deadline and offer to make it easy by sending the donation form or collecting the item.