Liz, the video clip Kater posted was a great way of doing it - IF your cat is that mellow. It's a different matter if they put up a fight, but in any case, it's a good idea to be behind the cat. I normally have Fister in the window sill (hip high). I lean over him to stroke him first, and have the pill ready, then, I put my finger under his front tooth to open his mouth and pop the pill in. It usually works.

At this point, give him a kiss on his pretty little nose, the amazement will make him swallow - or stroke him on the throat until he does.