This is what I do when I workout to gain energy:

1. Recognize that I'll be more productive if I go workout. There's no point in trying to think lazily.
2. Put on my exercise clothes. Go outside.
3. Sprint (http://www.laststopfatloss.com/the-complete-guide-to-interval-training-infographic). Imagine myself doing something fun while doing it. Nicholas Taleb says that he imagines chasing wall street bankers.
4. Take a cold shower.
5. Post-workout meal. (Carbs. Protein shake. Creatine. D-Ribose. BCAAs).
6. Get back to my desk about ~40 minutes later.