Yeah, Like Shannon said- put the food item up nice and slow-and it does seem to work best right below the level of their head.
Then sometimes I move it against their lower lip in a very, very slow and gentle circular motion, if it doesnt freak them out. sometimes they will slowly turn their head sideways and start to eat. That one worked especially well with a rosy boa I was helping to get feeding.

And I have some snakes that only eat from the comfort of their hidebox. I have to enter the cage as quietly as possible, and gently reach the food item into the hidebox with my hemostat, then they will take it. If I disturb them at all- its a no-go.
For those types of snakes, a small, low profile hide works best- one just big enough for them to fit under- makes them feel more secure. Not that this is necesarily what your snake is like- but I thought I'd mention it.