What are the most common quick-fixes in terms of energy efficiency?

We often find quick solutions to energy efficiency lie in critical cooling and air conditioning systems and the air flow path within the server room or datacentre. Typical issues are poorly sealed floor tiles or rack cabinets with missing or poorly fitted blanking plates. Other solutions to poor energy efficiency figures (leading to high PUEs) include not upgrading to the latest energy efficient solutions including file servers, cooling systems and uninterruptible power supplies.