When
you are prepared to paint a room in your house, you should
follow these basic steps:
Remove what items you can including: screens, curtains,
outlet plates, switch covers, hardware from windows and
baseboards.
Cover what you can´t remove: fixed carpets, large pieces
of furniture, etc. Make sure you have enough drop cloths
to cover everything.
Repair any imperfections, holes or cracks.
Scrape and sand areas where paint is loose.
Sand the entire surface.
Wipe off all the sanding dust.
Spot prime any areas where you need to use spackle, or
where you sanded through to bare drywall.
Remove what items you can including: screens, curtains,
outlet plates, switch covers, hardware from windows and
baseboards.
Cover what you can´t remove: fixed carpets, large pieces
of furniture, etc. Make sure you have enough drop cloths
to cover everything.
Repair any imperfections, holes or cracks.
Scrape and sand areas where paint is loose. 
Sand the entire surface.
Wipe off all the sanding dust.
Spot prime any areas where you need to use spackle, or
where you sanded through to bare drywall.
