General recommendations and advice for oral cleansing
On the importance for dental health of flossing, interstitial and tongue cleaning and the risks of overbrushing...
Interstitial cleaning to remove bacterial coatings from the crevices between adjacent teeth
There are several theories regarding the question where caries (tooth decay) actually starts, with the two major contestants being the "endogenic" versus the "bacteriogenic" theory of cariogenesis1: one of the latter maintains that tooth decay begins between the teeth, in spots where food rests can't be removed by brushing and which subsequently fall prey to bacterial activity and their acid waste products.
In fact according to the German Stiftung Warentest magazine, a whopping 40% of the total tooth surface is located between the teeth. Here is where the often-recommended flossing comes in for which various floss products are available. (Please note however that Dr. Hulda Clark for instance warns against commercial floss varieties and writes in this context: "Don't use floss; use 2 or 4-pound monofilament fish line2. Floss has mercury antiseptics (with thallium pollution!.")
To help clean between teeth, one can also use an oral irrigator such as the Waterpik, special interstitial brushes (interdental brushes) or a toothbrush such as the Perio toothbrush whose bristles are specially designed to be able to penetrate between the teeth (although I don't think the latter will/can remove all interstitial deposits). Interdental brushes are small, available in different widths and clean between adjacent teeth (be careful to avoid forcing the brush into the crevices). Failing all the foregoing, in my experience, repeatedly straining water through all my teeth and/or oil pulling dislodges much/all debris from inbetween the teeth.
Cleaning your tongue
The tongue can harbour many bodily excretions which as hinted at by their smell, aren't healthful for the body. One can gently remove these layers by getting a specialised tongue scraper or cleaner (which reaches far back to the tongue's root), but simpler implements (such as a tablespoon or your toothbrush) will help keep your tongue clean as well. In a pinch or hurry, even your own teeth or fingers can help cleanse part of your tongue.
Interestingly, as proven by scientific studies, the tongue can also be swarming with "caries bacteria" (cariogenic pathogens) such as streptococcus mutans. See for instance "The effect of tongue scraper on mutans streptococci and lactobacilli in patients with caries and periodontal disease" at www.ncbi.nlm.nih.gov/pubmed/16032940 and "Tongue scraping as a means of reducing oral mutans streptococci" at www.ncbi.nlm.nih.gov/pubmed/14969377?dopt=Abstract.
The first study showed a significant decrease in salivary levels of streptococcus mutans and lactobacilli after twice-daily tongue scraping for a period of time, with the added bonus of reduced bad breath. The second study aimed at determining the most effective oral hygiene technique for reducing streptococcus mutans counts, with the three treatment options investigated being tongue scraping, rinsing for 30 seconds with a saline solution (salt water) or applying a listerine strip, respectively. Surprisingly (or not), the winner was tongue scraping, with salt water rinses coming in second and the least effective hygienis measure being the listerine strip.
Studies such as the above really bring it home just how important it is to clean one's tongue.
Overbrushing causes enamel damage
Beware of too much of a good thing. You can damage your enamel and possibly gums by brushing too often or using a brush whose bristles are too hard too vigorously. Similarly, even natural materials used for cleansing purposes may be too abrasive if overused or if your teeth are "delicate". Don't be fooled by the seeming hardness of your teeth and observe your teeth to see whether they are of the strong or weaker type. One indication of weaker teeth can be incisors that are flattened (abraded) at the top. That said, teeth of course can both be weakened and strengthened, such as via diet etc.
Avoid brushing immediately after contact with acidulous foods or drinks, simply rinsing your mouth with clear water may be best (and perhaps adding some baking soda to raise pH). The same may be true after eating sugary foods. If you have them available, xylitol products may be very helpful.
1 Compare eg Dr. Herbert Shelton on the true causes of tooth decay.
2 Personally I use simple thread when I do floss.