“Dry them out”; use glycopyrrolate (no central effects). How to use local anesthetics and more… emcrit.org  Listen to the podcast here.

EMcrit recommend: Airway Regional Anesthesia for Awake Fiberoptic Intubation, Simmons et al, Regional Anesthesia and Pain Medicine 2002. Read the review article here.
Fibreoptic vs videolaryngoscopic (C-MAC(®) D-BLADE) nasal awake intubation under local anesthesia. Kramer et al. Anaesthesia. 2015 Apr. Read the abstract here. Dr. Michael Bailin demonstrates an awake endotracheal intubation at the Massachusetts General Hospital.

I also recommend these two: Flexible scope intubation for anesthesia, Hagberg et al. UpToDate; Literature review current through: Jan 2016 (updated: Nov 16, 2015). Read more here. Regional & Topical Anesthesia for Endotracheal Intubation, NYSORA. Read more here.