How to fix Macbook Air boot into a black screen after sleep?

It's been the 2nd time I encountered the problem that my macbook air boot into a black screen, I fixed it last time by phoning my Mac Buddy. This time I asked Google how to fix it, and from all the suggested method, the below one is fixed my problem.

Try a PRAM Reset to Resolve the Black Boot Display 

PRAM reset can often do the trick, as many of the commenters on this article can attest to. As a potential solution to the black screen on boot, this is done upon restarting the Mac similar to an SMC reset: Reboot the Mac and as soon as you hear the boot chime, hold down the Command+Option+P+R keys together When you hear the boot sound again, the PRAM has been reset so let the Mac boot again as usual At this point your Mac should boot again as usual and no longer have the black display, loading Mac OS or Mac OS X as usual.

Further reading: http://osxdaily.com/2014/11/22/fix-macbook-pro-booting-black-screen/