Having recently picked up a cheap didgeridoo from a charity shop I have been trying desperately to grasp the concept of circular breathing. Circular breathing allows you to constantly have air leaving your mouth, to make the drone sound on the didgeridoo, whilst also taking air in through your nose. It has taken me about a week to finally nail the technique thanks to an intensive day of practice yesterday. Now I just have to take the technique to the didg to get that constant drone.
Below is the best circular breathing lesson that I found on YouTube. There are two parts to it but I can guarantee that if you follow each step, just like he says multiple times, you will get it.