The dentist will check if your teeth are suited for whitening and if there are any issues which need to be addressed. For example, any fillings on front teeth will not whiten and you will more than likely be required to have these replaced to match the colour of your new smile.
One of the tried and tested systems we have been using for a while is the patient take-home kit. It is effective, economic, reusable, low maintenance and you control how white you would like your teeth to be.