In order to make sure the game runs as smoothly as possible, please ensure that you are not forcing any settings through your graphics card's control panel.
Below, you can see where to set the ATI Catalyst Control Center and the Nvidia Control Panel to use application settings.
Make sure that "Use application settings" is checked for Anti-Aliasing, while "Anisotropic Filtering", "Adaptive Anti-Aliasing", and "Catalyst A.I." are all disabled.
For Nvidia, you can set custom settings for individual applications. Please ensure all graphics settings for RIFT are set to "Use global setting (Application-Controlled)"