+1 for the baking soda.
Baking soda toothpaste & a sonocare toothbrush. I don't do it all the time, but a few times a week with the sonocare and other times with a normal toothbrush and it's great. I haven't had my 6 month checkup in... err.... uh.... gee.. hope my wife isn't around...

but my teeth are white. If you have some buildup already, then you may need to do it for a couple of weeks. I also buy that hippie toothpaste that doesn't have flouride in it, but I think it's the important thing is the baking soda that has enough abrasive in it to get the gunk off.
ps - are you eating something that puts a film on your teeth? I don't know all the terminology, but there is a kind of buildup that you can scrape off if you haven't had your teeth cleaned in a while that seems to be the thing that gets stained. That buildup might collect faster with certain kinds of foods. If you use the soda it will grind the film off and you should be in good shape.