Should I wash chicken before I cook it?
If you are talking about chicken parts, the answer is no. For one thing, the bacteria which can make you sick are destroyed when you cook the chicken, not when you wash it. Also, no matter how careful you are, the more you handle raw chicken in your kitchen, the more you increase the risk of cross contamination in your kitchen. So you want to handle the chicken as little as possible.
You do want to rinse out the cavity of whole chicken, mostly to get rid of the pink liquid (which despite appearances is not blood), and any loose bits floating around inside the chicken. When rinsing out the cavity, be sure to remove your sponge from the sink first (to avoid contaminating it), and rinse the chicken with cold water. Have a plate or pan right next to the sink so you don't end up dripping the wet chicken across the counter or floor.