Cunnilingus is basically stimulating the female genitals using the tongue and lips aka oral sex, eating pussy, giving head, going down. Before explaining how to get down like a pro, it is important to understand that each female is created differently. In terms of the shape, color, size of the labia, smell, taste, pubic hair, generally how the genitals are structured. Also, note that oral sex can still cause Sexually Transmitted Diseases and so dental dams should be used.
There are various techniques out there, you should communicate with your partner on what turns her on the best. Ensure not to go heavy on your partner. Start slow and depending on whether she wants it faster, then you should go faster. Take your time while eating. You are in for a long haul and if need be, change your position.
Some of the techniques that can be explored are up and down movement with the tongue, lick the hood going back and forth, going in clockwise circle, counterclockwise circle, engulfing your mouth all around the clit and then softly sucking it.
While eating, try not to go from back to front as this can introduce infections to you and your partner. And lastly, eat with your hands. You can use your hands to stimulate other parts – stroking or fingering.
To be honest, there is no one size that fits all. There is no one way that can make your partner climax. Just keep trying and understanding what your partner really wants.