Apple has just announced a new program for beta testing OS X alongside the iOS 7.1.1. update. This program allows non-developers to download OS X betas before they are available to the public. Until now betas have been restricted to only developer accounts which cost $99 per year.
You can apply for the beta at the source link down below. Apple requires anyone who uses this program to sign a confidentiality agreement which prevents users from disclosing, publishing or disseminating confidential information from the betas to users not in the program. After signing that agreement users are asked to make a backup of their Mac in it’s current state and then downloading a special app which allows the Mac to download the Beta updates. Updates will be delivered through the App Store similar to regular OS X updates.
Source: Appleseed Program