'Efficiency' might be a controversial word in cycling, but it is something that you can work on. Here are some key training sessions.
Cycling efficiency might refer to several aspects of riding: your pedal stroke, your riding style, and, how you burn fuel.
How can you work on these aspects? Focussing on riding in the saddle is one great way of doing this as it uses far less energy than riding out the saddle for sustained periods. Pre-breakfast rides are also a great way of improving how efficient your body is at using a variety of fuel sources - this session is great for training your body to utilize fat. Tempo sessions and training at the effort level that you'll spend most of your time racing at, will help you to used to those effort levels and therefore become more efficient.