In person. A short, specific ask from someone who turns up with the donation form is the most effective approach, followed by a phone call, then email.
The specific thing they're best placed to give, such as a dinner for two from a restaurant or a one-night stay from a hotel. "Anything you can spare" rarely turns into a prize.
Recognition they can see: their name on your campaign page and in your event program, a mention from the stage and a tag in your social posts.