The most important things to consider when it comes to power consumption are the external components which you connect to Bela. Connecting speakers to the on-board amplifiers will significantly increase power consumption, as would connecting something like an LCD screen or an LED array.
There's not a whole lot that can be done to lower the power usage of the BeagleBone while it is running a Bela program, although switching off the analog or digital i/o (which can be done through the command line or IDE settings) if you aren't using it may help a little.
