How can I make my checkout or payment form shorter?

A few form settings shorten the checkout page:

1. Show the card number, expiration and CVV on one line instead of several lines.
2. Turn off the order summary (order total) when the form sells only one product.
3. Keep product descriptions short, because they are shown on the form.
4. Use a two step order form, which collects name, email and phone on the first step and makes the payment step smaller.

You can also sell several products from one form: the buyer picks a product from a selectable list (not a dropdown) on the second step. That is far less maintenance than one form per product.