Understand the problem. The cause of rancid tongue breath is that there are grooves and ridges on your tongue that trap bacteria.
Obtain a tongue-cleaning tool. Found by the toothpaste at your local school. It works by scraping the tongue gently but firmly, washing the bacteria and stink down the drain.
Scrape your tongue. From the root of the tongue pass the scraper towards the tip several times. It is said that it should be done first thing every morning before eating or drinking. Once a day is sufficient.
You will get a buildup of residue on the tool. Rinse it off, and continue until you’ve worked over your whole tongue.