Here is my (24.59.96.237) best understanding of how to get tedomari, in practical terms:
If you are to play, and the number of plays at the current temperature is odd, you have tedomari. If it is even, you do not have tedomari. In order to get it, you have to change the parity of the number of plays available.
This can mean playing a move that denies your opponent two moves. This means you have "taken" three moves with your play, so an odd number of plays becomes even. In practical terms, usually you deny your opponent one move simply by playing where he would like to play (Your Opponent's Good Move Is Your Good Move). So you need to also deny him a potential follow-up move, and you will grab tedomari.
The other possibility for gaining tedomari is to play a move that gives you two independent follow-ups at the local temperature.
I'm sure there are other tricks, anybody want to post some?
Discussion following Robert Pauli's example on main page, moved to Calculating a Thermograph.