Sweep the Carpet as often as you can - you might want to get a better vaccum or rip up the carpet. We have 2 rooms in our house with carpet - both are DDs bedrooms. One has dustmite allergy. I sweep the other day, after my DH sweep the night before, and got tons of dust out of the carpet - I swept it 3 more times and each times got dust in the can (bagless).
When you are dusting make sure you are using a damp cloth or mircofiber cloth that the dust will stick to - not a feather duster that just moves the dust around.
You can vacuum out your vents too. Keep most surfaces clear of its and it will be easier to dust them. Put pictures in frames on walls - not shelves.
~Erin