Most people with sleep problems don't make it to 20 without drifting away and loosing count. Thats when you notice your drifting. Naturally you'll get a little excited that it worked and you've found a way to fall asleep easily. Feel the appreciation every time you drift off and mix up the count. Love it because you know your going to be falling asleep soon. After messing up the count, I think it's important if you always start at the number you distinctly remember saying in the correct order before you drifted away. If the last number you remember before skipping to 20 is 17, go back and start at 17. Big bold white letters over the black endless background, think of nothing else. Sweet dreams

I've never put much stock in counting sheep, but had sleep issues which led to me trying many different things. This is the most successful way I know to fall asleep and 100% of the people i've shared this with swear by it. It's simple and effective. 
What your going to do while laying in bed is close your eyes and see the darkness. Then picture numbers fading in while moving towards you. Bold white numbers over a black background. I made this video as an example. iMovie would not let me make the numbers bigger or zoom in for some reason, so picture zooming into the numbers until there really big. Almost taking up the whole black background. Start your count on an inhale and really focus on the number and nothing else. That is very important. Other thoughts may come in especially if you have a lot on your mind or you have physical pain. Have the number start small and grow like it's moving toward you. By the end of your inhale the number should take up most of the black background. Watch the number fade away on the exhales. 

How to Fall Asleep