First of all you must realise that there are some limitations. Teeth whitening only works on natural teeth, so crowns and fillings will not be affected. Mostly this kind of work is on the back teeth so you can discard this as many people only whiten the front teeth. . Obviously if you have a crown at the front you will have to think carefully about replacing it so that it matches with the colour of your newly whitened teeth.
Then there is the sensitivity issue. As people get older the sensitivity issue increases, this is mainly due to receding gums and maybe some hairline cracks in the teeth. To over come this you can purchase the teeth whitening gel in different strengths, from 22% up to 36% and even by special order 45%. The higher the number the stronger the gel is and the quicker your teeth will whiten. For some people that would be too much and you can get the same results using the weaker gels but it will take longer.
For most first time users it would be good idea to start with the weaker gel and work up to the stronger gel. If you feel confident that you don't have any sensitivity issues there is nothing to stop trying the stronger gels and if this works well for you stay with that strength but reduce it if you have any adverse effects.
It is always a good idea to get into the habit of using remineralizing gelafter you have whitened your teeth.
Remineralization helps to protect and strengthen the teeth.
Remineralizing Gel: helps with sensitivity and strengthens tooth enamel post bleaching.