I have used detox foot pads, so I can speak from my experience with them. I think it's definitely a good idea to try a free sample first, but keep in mind that this really isn't an overnight process. To use detox foot pads as they are intended, you would need to use them for probably a minimum of every night for two weeks (and most likely longer). According to the instructions, you are supposed to keep using them until the pad is still clean when you remove it in the morning.
There is some controversy over how effective these are and about whether or not it is just the stuff inside the pad that makes the greenish-black, sort of greasy results that you will see in the morning. I'm not an expert and can't say whether or not that is true; however, I can say that I used them every night for one month, and it never got to where the pads were still clean in the morning. So, either I have a heck of a lot of toxins in my body, or something else is going on.
I just found some more of these pads when I was cleaning out my closet the other day, and I set them out to do another round of detoxing. So I suppose perhaps that is evidence that I at least believe in their effectiveness enough to give them another try, rather than just throw them out.
If others do this, I would love to hear about your results!