L.D.
I taught my children when they were 6-years old. What I did was gather up a number of food items of various sizes like rice, sprinkles, mini M&Ms, skittles, and a big glass of water. Starting with the smallest item, the sprinkles, I'd put a sprinkle on my tongue and showed them, then a big drink of water, then opened my mouth to show them how the sprinkle just washed away down my throat with the water. Then I had my child do the same thing. Once they mastered sprinkles, we tried it with a grain of rice and the mini M&M and the the skittle. Once they master the skittle, they are pretty much ready for pills -- unless they are horse pills.
Hope this helps.