In uniform salute, in civilian clothes while in the army stand at attention, in formation the soldiers stand at attention while the officer salutes. In civilian life you are technically supposed to stop while it is being hoisted or lowered if memory serves me correctly, but I doubt many actually do so..

And generally outside of the army as long as you don't act in extreme disrespect to the flag I doubt anybody really cares what you do when the flag is hoisted or lowered.