If it's fabric, you can spray it with a mild stain remover, put it in the washing machine in a pillow case and hang it to dry. I did that with one of my poppy bags and it came out looking brand new.
Coach also makes a fabric cleaner(10 bucks at any coach store) but it only works if the spot is new, although it'll sometimes help with older spots.
If you Google how to clean coach bags you'll get results from purse forums with ideas on how to clean other kinds of material.