Apple has set up an FAQ site to help businesses get set up with Apple Pay. They've also clarified compatibility between the system and the Apple Watch.
The new FAQ goes into detail about how to get set up with Apple Pay. It covers the obvious, like needing a contactless payment terminal, but also lesser-known aspects, such as the lack of fees, the fraud policy, and how to let customers know that your store supports Apple Pay. From the Merchant FAQ:
How do I let my customers know they can pay with Apple Pay?
Display the contactless payment symbol and the Apple Pay acceptance mark prominently on your point of sale terminal to let your customers know they can use Apple Pay in your store.
Display the Apple Pay acceptance mark prominently in your door or window.
Apple has also made some changes to the main Apple Pay website. A list of merchants supporting the payment service is now located on a separate site, found by following the Where to Use Apple Pay link at the top of the main Apple Pay page.
While Apple mentioned that Apple Pay would be supported on the iPhone 5, 5c, and 5s through the Apple Watch during their September 2014 event, they have now made that clear on the Apple Pay site as well. The bottom of the page now features a compatibility chart, which confirms that you'll only be able to use Apple Pay on older devices in physical retail locations, with in-app use remaining restricted to the iPhone 6 and iPhone 6 Plus.