How to control fps in OpenGL application.

Hi,

I know that there are many ways to control the fps when implementing an OpenGL ES application.

(ex. eglSwapInterval, sleep, polling, etc..)

I'd like to know what is the common way, among other things.

For example,

what is the most optimized way to render at 30fps on an LCD with a refresh rate of 60Hz?

Also, what is the way to control FPS using eglClientwaySync API?

Thanks.