From Mike Chan at the Canon Digital Learning Center:
Memory card management during a shoot is very important and we all strive to avoid that sinking feeling when you take a memory card out of your card wallet, insert it into the camera, format the card, take a shot and realize that you inadvertently overwrote a full card. A lack of battery management is not AS catastrophic, but it can mean missing a series of key shots while trying to find a fully charged battery out of your bag.
There are many different methods to battery management and it is up to you to decide what feels comfortable. For example, Canon Explorer of Light Vincent Laforet mentions in his time-lapse tutorials his method of putting colored gaffers tape over the battery contacts as a visual cue for unusable batteries. For users of the Canon LP-E6 battery (found in the EOS 60D, EOS 60Da, EOS 70D, EOS 7D, EOS 6D, EOS 5D Mark II and EOS 5D Mark III), Canon Inc.’s engineers have built a battery management system into the yellow battery cover.
See the entire article on Canon Digital Learning Center.