Wear a pair of old socks on each hand to dust. It is efficient if using both hands and cheap and you can wash and reuse them. You can also use old socks on duster and sweeper handles instead of buying disposable refills and pads.
Hate dusting Venetian blinds? Fasten a cloth around each end of a set of tongs with rubber bands and tackle those slats two at a time. Another easy way is to use the brush attachment of your vacuum cleaner and vacuum the blinds.
Get the dust off knickknacks with compressed canned air or a blow dryer.
Wrap old pantyhose around the head of a broom then let the handle help you reach underneath a couch or cabinet.
Reach tight places by wrapping a dusting cloth or sock around a ruler or kitchen spatula. The handle will give you an extended reach.