To open the lungs, take deep breaths in and long exhales (as if they were blows on a clarinet) trying to keep the tension on the lip, on the diaphram and abs but loosing all the tension on shoulders, fingers, chest and arms. The blow has to stay as linear as possible (and so the note).
By Riccardo Acciarino
Then warm up the fingers, imitating musical scales and moving between all the different positions in the lightest way possible.
Remember that the ground is your best friend and the only very stable thing connected to the moment (of the concert). Close your eyes for a few seconds and imagine a little but really shiny light on the horizon, then I place it at the end of the hall where the last person of the audience is seated in your imaginary solo shw, and mentally play a final note in your clarinet to reach them.