I found the best DIY tip - whitening teeth with activated charcoal! All you need to do is to mix activated charcoal with some water to create a paste. Put the paste on your toothbrush and brush it on your teeth. Leave it on for 5 minutes and than rinse off. I bought activated charcoal in tablet from at my local pharmacy in Stockholm. It´s an effective, cheap, simple and pain free way to whiten your teeth.