Lorna Mitchell has a quick post related to some of the OAuth work she's done on both sides, consumer and provider. This latest post relates to the OAuth pages and endpoints that are needed as a part of the authentication process.

This article uses the pecl_oauth extension and builds on Rasmus' OAuth Provider post. [...] OAuth has a little more baggage with it than just passing a username and password to an API.

She lists the five things you'll need for your service and talks a bit about the registration process and how the consumer key/consumer secret keys are generated. There's no strict definition on them, so her example uses a combination of sha1, mt_rand and substr to get the job done. She also includes a sample "consumers" table for your reference.