"A surprisingly large number of electrical products—TVs to microwave ovens to air conditioners—cannot be switched off completely without being unplugged. These products draw power 24 hours a day, often without the knowledge of the consumer. We call this power consumption "standby power."
An individual product draws relatively little standby power (see here for examples)
but a typical American home has forty products constantly drawing
power. Together these amount to almost 10% of residential electricity
use." (emphasis added)
Among the 40 products that constantly draw energy (have stand-by power) when you left it unplugged into an outlet, i.e. cell phone charger, computer, TV, kitchen appliances.
So using power strip, turn the power strip off or unplugging it from an outlet when not using it, maybe the easiest thing that one can do.
If you're on the market for new gadget, be on the lookout for information on how to buy products with low stand by power.