Chocolatier Michael Recchiuti says that everyone, even the experts, finds chocolate intimidating. Here is something he told us while we were developing our recipes, refining our process, and tempering a lot of chocolate.
Chocolate is an organic medium, which has few ingredients, but [is] extremely complex in crystal structure. Practice and patience is the only way to achieve a good temper and positive results. If you mess up the temper, you can always remelt the chocolate and try again. It is worth the frustration; all of us at Recchiuti go through learning curves every day, that’s what makes it so interesting to work with chocolate. Chocolate is like playing music: Practice will allow for better results and [a] higher level of comfort the more you work with [chocolate]. 
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For white and milk chocolate: Heat to 116 to 118 degrees Fahrenheit; cool to 80 degrees Fahrenheit; reheat to 85 to 87 degrees Fahrenheit.
For dark chocolate: Heat to 118 to 120 degrees Fahrenheit; cool to 80 degrees Fahrenheit; reheat to 88 to 91 degrees Fahrenheit.