Tooth bleaching. It depends on what your goal is? If you want a gradual whitening, at home bleaching would be a good option. If you want an immediate result, in office bleaching would be the treatment of choice.
Custom trays. Custom trays made at your dentist work best. Zoom and other products that utilize a light are very popular, but they are not any better. Intact, the initial "whiteness" is due to dehydration, and changes back quickly. With custom trays, you can use different % of gel depending on how sensitive your teeth get.
There is no best. Technique. It depends on how quickly you want to whiten. The professional in-office whitening systems work very well and provide the immediate "wow". The take home kits take 7-10 days to give good results. Consult with your dentist for professional kits versus the otc kits.