The first thing is to seal your lips inside the mouthpiece and buzz your lips in a fairly relaxed fashion to create the fundamental note, often called the drone. Many people around the world like to just play this basic note, and change the sound by emphasizing different harmonics with the shape of the mouth and movements of the tongue, like, “weeeooooaaaaaow.”
While Yolŋu use the shape of their mouths to affect the tone in subtle ways while playing, they do not spend their time playing these slow sounds and experimenting with these swirling high harmonics. It is all about the rhythm. But they do tend to start the yidaki with short notes, as if warming it up, then play a short drone before the rhythm begins. Keep in mind there would normally be singing too, not just yidaki.
Many people around the world play the didjeridu to the side of their mouths rather than playing straight on. A very few older Yolŋu who adopt certain softer styles of playing have been known to do this, but almost all will always play straight on, as it is much more appropriate for their style, which involves strong use of the tongue to aggressively push air straight out the mouth.
Marritjŋu Gurruwiwi and Mirrwatŋa Munyarryun playing yidaki – straight on!