Ama is the residue of undigested food. It's not a pleasant business, sticky, whiteish/yellow, smelly. In short, it's toxicity in the body, and as such Ama is a major cause of dis-ease in the body. Ama coats the shrotas (the body's physical and energetic channels) and the body attempts to clear this toxicity out via any means possible. The easiest means usually involves an opening in the body.
Wondering if you have a lot of ama? The check is pretty easy. First thing in the morning, upon waking, make your way to the bathroom mirror. Stick out your tongue, what do you see? Whiteish-yellow coating, sticky, smelly? Yup, ama. Wait too long after waking to clear that ama, and it makes its way back into the body. You can help your body clear that ama out though. Besides righting your digestion, you can clear the ama that has already accumulated. Enter the tongue scraper.
This magical piece of stainless steel will scrape the ama off the tongue and, with it, stimulate the gastric fire and digestive enzymes. While some think that brushing their tongue will accomplish the same thing as scraping, ayurveda actually understands that brushing the tongue works the ama back into the body, adding to the toxicity in the body instead of lessening it. Gently scrape from the back of the tongue to the front, until you have scraped the entire tongue (7-14 strokes).
With some attention to your tongue you'll receive important feedback from your body. How did what you ate or drank yesterday, or the time of day you ate effect your digestion and accumulation of ama? You'll see days where your tongue looks clean and clear, you'll see days where the ama seems endless. Use this feedback to inform your choices and as you see your ama decrease, see your vitality increase.