This is a good idea:Cleaner Carpet

There's vacuuming and then there's vacuuming. If you
just
run the vacuum over the surface of the carpet
quickly, it
will only pick up dirt on the surface. Finer
particles work
their way down to the carpet backing and build up,
providing the ideal environment for flea eggs to
hatch and
thrive and allowing the carpet to just keep getting
dirtier.

Vacuum in slow motion--really, really slow motion.
This
gives the machine the chance to pull dirt to the
surface.
Vacuum in several directions wherever possible. Pay
special
attention to traffic areas, dog sleeping areas, and
places
where your dog jumps down off of furniture.

- Paula Dupy