An important point, espeically with a power hungry smartphone. There are any number of other tweaks--and even apps!--to let you squeeze every last electron of battery life out of your phone by adjusting settings or eliminating unnecessary processes that consume power.

Airplane mode is better than turning your smartphone off because really, your smartphone is just a miniature computer, and it takes a considerable amount of juice to boot it up from an off-state, and we all know how much activity goes on when we're waiting for a computer to boot up.