Perhaps the most efficient and powerful energy practice I know is learning to breath.
Yes, I know it sounds strange. We all do it, but it's mostly an unconscious act and so we don't get the wealth of benefits available to us when we make it a conscious activity.
When I speak of breathing, I mean the kind of breath that you feel expanding your belly. The type that takes more than a couple of seconds, but that can be done anywhere, at any time.
The key to making breath productive (that is - beyond basic living) is having some focus on what you want it to do for you. When our thoughts and body are working together, we can accomplish a great deal.
Here are some topics that can be effective to use with your belly breathing:
Relaxation
Doing what I'm doing with ease and flow
Feeling loved and sending love to others
Making a decision about something
As you focus on a topic, take in the breath and feel it going through your whole body, feel it nourishing your system, energizing your limbs and bringing a smile to your face. Allow yourself to take that brief moment as you relish the entire experience.
Notice the change in your approach to whatever is happening for you after a conscious breath. How does it feel for you?