Crest whitestrips are the first to go in my opinion. There are 2 kinds of CWS you can try. One over the counter like any drug stores or grocery stores would carry OR ones you can specially order through your dentists. Latter is the stronger version of the Crest brand but is significantly less abrasive than the Britesmile, Opalescent or ZOOM (all are in office whitening treatments, which involves laser procedure or trays that you do in the office and at home).
I have had peopler tell me they get sensitivity from in office treatment whitening treatments but very rarely from white strips. I have seen some good results of Crest whitening strips because usually people do the smile area only (the teeth that you see when you smile) vs back teeth (show naturally shade of the teeth).
Sensitivity that results from any whitening procedure usually lasts 2 days to a week. But this also depends on people. Some people discontinue after lil while because of the discomfort but I/people still notice slight diff in the shade or the teeth. If you get sensitivity use any fluoride rinse OTC or Sensodyne tp (<- tastes yucky I know) These usually help somewhat. with severe sensitivity u can ask ur dentist to write u a prescription for Fluoride tp or rinses that you can use at home that are stronger in conc.
With all other baking soda stuff, peroxide rinses and all that... you can try these to maintain the new shade, hence minimize the stains from coming back or keep teeth from turning back to orig. shade. Moreover, you probably need to control what you take in. i.e. coffee, soda, wine or tea. Some say chocolate also but that I can't say for sure.
I think britesmile has special mouthrinse, toothpaste, some sort of paint on thing (touch up pen) you use at home after the in office procedure and gums that you chew to maintain the new white smile!