In order to improve your playing technique, you should first learn how to circular Breath while playing. You can't be a professional didjerido player if you can't circular Breath!

Circular breathing is continuously expelling air through the mouth while breathing in (and sometimes out) trough the nose. It is a skill used by didjerido players to create a continuous drone.

Blow out air through your mouth, using only your cheeks to press the air out. After doing that try to take out air trough your nose while taking out air trough your mouth. Then practice inhaling air trough your nose (don't stop taking air out trough your mouth.) do that several times till you succeed. While you are breathing in, squeeze your cheeks to continue pushing air out through your lips. Bagpipes work on the same principle, except you have a bag under your arm which you fill up, then when you want to breathe, you stop blowing into the bag and while you are inhaling the bag is squeezed by the arm to continue the airflow.

Practice step by step:

Practice that by blowing air on your hand, feeling the airflow that comes out of your mouth.

Step one:
Exhale for about 5 seconds then make sure your cheeks are full with air, then stop exhaling and on the same time squeeze in your cheeks so the air continues to flow out of your mouth. You will eventually run out of air. Take a breath and start again. Soon you will be confident with squeezing the air out of your mouth and keeping the air on your hand.

Step two:
Now, while you are blowing air out of your mouth, breathe in through your nose. Don't try to restart exhaling just yet. Get used to the cycle. Breathe out, pump with the cheeks and inhale. Soon you will be used to this system as well.

Step three:
Try to restart the exhale cycle. The major problem is going to be balancing how much you breathe in with how much you breathe out, so don't worry if you run out of breath or you can't expel all the air in your lungs fast enough just yet. Relax and get into the cycle - exhale, pump and inhale, exhale, pump and inhale. Remember to fill your cheeks with air while you are exhaling.

Step four:
Practice. Keep airflow going for a minute, then two and more. concentrate on balancing the airflow in and out. You should be able to breathe in and out through your nose while maintaining the airflow. Practice that by filling your mouth with water and spraying it slowly (over about 15 seconds) while breathing in and out through your nose.

Now you are ready to transfer to your didjerido! Remember that your lips need to keep vibrating all the time and that you don't need much air in order to keep a good continuous drone sound. At the beginning you might have some short break between one breathing cycle and another but practicing will solve that.