What is the best way to detox?

i really just want a good cleansing for the new year. i've got midterms & i'm getting clean from the green for track season coming up. i just want to get to a better, healthy state. i've heard detox can be used for losing weight (which would be nice) i'm not over weight, but i'm getting back in shape. i heard it can be just for cleansing your body. i'm looking for something i can use thats healthy, and i can get at GNC or something. does anyone know a good one? or maybe a method of detox & not a kit?