Hi, Stains produced by smoking
habits over several years can be pretty adamant ones. The first thing you need to do is quit the habit, to allow any subsequent corrective measures to be effective, and maintainable. Once that bridge is crossed, possibly get a thorough cleaning of your teeth. This should improve your oral condition in general, and get the teeth looking much better as well. Further improvement can then be achieved by various means, depending upon the clinical situation, and your desires. You can discuss these with your dentist
. Hope this helps.