Always have a clean sheet to start with. And since this is your bedroom, feel free to personalize it all you like. Pick the color you like best, pick the color - or even colors, why have a limit at all? - that reflect your personality. Be it the white neutral colors of the people who like to fill in the blanks with their imagination, or the darker shades of the melancholic types, or even the vibrant colors of the social, hyperactive, and energetic people, just pick what suits you best and start painting.
After the paint dries off, it is time for some cleaning. Take out the duster, wipes, and vacuum, and go wild. Do not forget to go from top to bottom so that you do not have to do carpet cleaning twice - once before you start, and once after you drop all the dust and cobwebs on the clean carpet. You might want to put a good medium-stiff bristled brush to work on the carpet to clean up all the hairs. You would be amazed at how many of them there will be.
Alternatively, you could go with a dependable and professional cleaning agency to take care of your bedroom cleaning, or why not even house cleaning while they are at it. The professional cleaners will get your house clean in no time, and in a much faster rate than you can.
Add new items to your bedroom, like a desk for a PC, or some shelves for your favorite or about-to-be-read books. Add a painting or two, or maybe a poster of your favorite actor or musician to add some life to those walls (yes, sometimes you can take advice from your kids for decorations).
Improve on the old stuff. Replace some furniture with better, or wilder-looking ones. Replace the night lamp with something fresher or more interesting than the same old night lamp you have seen everywhere - like a lava lamp!
With this your bedroom will have a fresh new beginning, and you can feel free to add whatever you feel right. And do experiment all you like - it is your bedroom, after all.
After all the cleaning and repainting, start to think style. Find a new place for the bed - the enclosed corner of the room, or the center spot to have a room focus, your choice. Find a new place for the wardrobe and dresser, and while you are on it, why not organize it so that clothes-finding is not an issue during this season.