Smoking can weaken the lower esophageal sphincter, a muscular ring around the bottom of the esophagus that relaxes and opens to allow food and liquids to make their way into the stomach, and then closes again. If this valve doesn't work properly, stomach acids can more easily wash up into the esophagus and throat.
The fix: Stop lighting up! The health benefits will far exceed esophageal sphincter-strengthening (think lowered risk of all sorts of lung diseases, cancers, premature aging and more), so use whatever method will work for you. For example, if keeping a record of bad habit helps you to break it, download this Smoker's Diary and use it to track your progress.