Chocolate is best kept in dry places without strong odours and with good ventilation. The temperature should be 18-20 degrees C (65-68 degrees F). Humidity should be below 50% as it causes sugar bloom, which is a grey or white layer of sugar crystals on the surface of chocolate. Sugar bloom generally does not render the chocolate inedible, but the taste definitely suffers. If chocolate is stored too cold, water droplets condense on the surface when it is brought to room temperature and this too can cause sugar bloom. This can be avoided by keeping the chocolate covered until it has reached room temperature. If chocolate is stored in a too warm place, fat bloom occurs, which also appears as a grey layer on the surface of the chocolate and is related to structural changes in the cocoa butter. Chocolate which has suffered fat bloom is also still edible, but again, the taste and texture will not be nearly as good.
Probably it's best not to be starving, since you might be craving the chocolate for the wrong reason! Also best not to be overly full as high-percentage chocolate can quickly get too much for the stomach. Ideally perhaps a few hours after you have last eaten, and without any strong flavours in your mouth. Have a glass of water handy to keep your palate clean.
Before you actually taste the chocolate, note how it breaks when you snap it. Chocolate should not be too brittle (it might be too cold if it is) but also not too soft - a quiet snapping noise is perfect. Also smell the freshly broken piece, noting any unusual aromas. You can often already tell good chocolate at this point.
The piece you eat should not be too small - this is important in order to let the flavours fill your entire mouth. However, the higher the percentage of cocoa, the smaller the piece should be, as it is generally harder to eat chocolate with a high cocoa content. For 70%, a square inch of average-sized bar should be about right, for 45% you might want up to double that, for 100% at most half.
When tasting you should let the chocolate dissolve a little bit first and wait for first impressions. A good bar will often have a striking first impression, after a few seconds at most. Then chew the piece (except for very high percentages such as 99% or 100%) and make sure the flavours permeate your whole mouth. Sometimes it is best to close one's eyes to concentrate entirely on tasting, but talking to others - after a short period of initial silence - who are tasting the same chocolate at the same time can be helpful to identify flavours one cannot place.
It is always helpful to note down one's tasting experience for future reference. Things to note should definitely include:
(b) The texture (e.g. dry, brittle, fatty, oily, smooth, soft),
(c) The finish (did the flavours disappear quickly or gradually), and
(d) The aftertaste (how long after swallowing the last remnants did you still have the taste in your mouth? Further things to note are the aroma (smell) and snap. Of course the percentage of cocoa solids, the origin of the cocoa, the manufacturer and the name of the bar are essential, but also look out for any indication of the bean (sub-)type used, added ingredients or special treatments of the cocoa.
In recent years the community of serious chocolate tasters has been growing rapidly and has gained widespread attention in the media. In 2005, Chloe Doutre-Roussel, then head of the chocolate department in Fortnum & Mason, published The Chocolate Connoisseur, heralding a ``chocolate revolution''. And in 2006 the magazine Wine & Spirit described the art of chocolate tasting as equal to that of wine tasting, and the complexity of flavours in wine and chocolate as comparable. This movement however already began in the early 1990s with the first single-origin bars from French chocolatiers Pralus, Michel Cluizel and Valrhona, and the foundation of The Chocolate Society in the UK in 1991. The website www.seventypercent.com has also been spreading the word and offers news, an online discussion forum and reviews of chocolate bars. In connection with this website, The Chocolate Connoisseur's Club runs monthly tasting evenings in London. Another very good option is to create your own chocolate tasting community, by picking a few interesting bars and inviting some friends - perhaps even as a regular event. Other people's tasting notes should be merely taken as an orientation. In the end the best thing is always to taste for yourself and develop your own tasting judgment.