Old and Crappy
Actual need for a gastric tube in the prehospital setting is rare. Anyhow, the gastric tube should be placed orally (nasal route is a risk factor for VAP). To help you can have someone perform a jaw thrust or you can use your nondominant hand to grab the mandible and distract it anteriorly while inserting the tube. Still having trouble? Just stick you finger in the back of the throat to help guide it. Be care not to force it if you're getting a lot of resistance. (In the past year where I'm working, a medicine resident caused a pneumo while placing a dobhoff tube, which managed to make its way past the cuff of the ETT and into a lung. OOPS!)
How do you recover from a mistake like that? Don't get me wrong, I'm not trying to say I could not have made the same mistake but I think I'd have to quit.