How can you eliminate or improve post nasal. drip?

Depends on the cause: Post nasal drip can be due to a deviated nasal septum, nasal allergies, sinusitis or stomach acid reflux. You should rinse your nose with saline morning and evening. If you have allergies, you may add an otc anti-histamine such as Cetirizine or fexofenadine. I do not recommend nasal or oral decongestants beyond a few days. Don't eat or drink 2 hours before you go to bed. If no better, see a phys.