I am a huge coffee drinker so I have always had really discolored teeth, just a little off white no matter the brushing. I tried other whiten methods, wanted whiter teeth so I tried this. The instructions are straightforward. You put them on for just 30 minutes, two times a day. I did mine at night before bed so that I do not eat anything to stain them again during the process. There are convenient because you can use tem while do other housework. However, it is hard to swallow or you do not want to swallow with these on. So you end up with a mouth full of spit or goo. Sometime the strips do not adhere to well and moves a bit in your mouth so that is weird. Another drawback is that they can burn or sting your gums so try not to get the strip on your gums because it does hurt. You have to be very careful and deliberate o how you place them on your teeth. The bottom teeth are easier than the top ones. In addition, it might hurt your teeth or make them sensitive. Someone recommend using a toothpaste for sensitive teeth during the whiten process to help with the side effect. this did help. However, all this is temporary. Maybe a few days to a week later my mouth was back to normal as far as the side effects. It did get whiter like I expected and I did get some complements on my smile. One friend even asked me what I did to get a white smile, I told her of course. She is a coffee drinker too. Basically when using there, use it during the two week where you don't have too much going on, so you don't forget to use them consistently and so that it is easier to tolerate the side effect. Then you should be good.