Teeth Whitening

im tryna go and buy one of those crest whitestrips type overnight whitening things. which one should i get?

which one lasts longest?
whitens most?
no sideeffects?

my teeth arent really bad… i just want them whiteI buy the Crest Whitestrips. The regular ones, I think that they run around $25. They work the best for me, considering I drink coffee and smoke regularly. For the price that is. I tried the new Listerine dissovlable strips and YUK! They are gross!