I'm not sure whether your problem is with the gag reflex (usually a good thing to have) or the pill sticking to your tongue - this method solves both of those problems.

First down some water to wet the mouth and throat.

Then take some more, and swallow about half of it.

Lean the head back, drop the pill in the mouth. If necessary move the head around as Dave says to keep the pill suspended.

If you need some more water, take it now.

Swallow.

Now take some more water in case the pill didn't make it all thw way down.

Now take a little more. Finish the glass if you like.

I can usually get even the biggest horse pills back this way.

If you have any trouble with this, replace the water with ice water, or better yet, milk, as cold as you can possibly get it, and take some extra sips beforehand. This partially desensitizes the throat, and horse pills should go down without a problem.

And if that fails, spray with some Chloroseptic to start and give it a few minutes to take effect. You should be able to swallow swords by this point!