C-Fix (fixed carbon content) - measures the amount of pure carbon in the charcoal. High quality charcoal should have a C-fix over 80 percent, and for briquettes this value should exceed 65 percent. 
Ash content - measures the amount of ash in percent. The lower the ash content, the better the charcoal. High ash indicates sand, minerals (stone or brown coal) or other unwanted substances that deteriorate the quality of barbecuing.
Water - high water content worsens the barbecuing characteristics and indicates bad quality.
Volatile matter - high levels of volatile matter indicate higher content of gases. High volatile matter causes flames, not a glowing barbecue surface. In the high-tech production process, the gases are burnt instead of the charcoal itself. 
Granulation - a good mix of granulation is essential for a long and even glow. Small pieces are used for quick ignition, whereas big pieces are used for long glowing. This is defined by the DNV and DINplusstandards. 
Hardwood - hardwood has better barbecuing characteristics then softwood. You can check if the charcoal is made from hardwood, as it produces a "metallic" sound when hitting the pieces against one another.
Automatic Closed Distillation System (ACD - system) - in contrast to other systems, you will receive a higher and more even distillation, measured by the C-fix level. ACD - system is also better for the environment since there is no usage of fossil fuels.