1. Just get started
If you just motivate yourself to put on the shoes, eventually, you're body will be ready to take on the task of the actual run. Slowly but surely, as you get dressed and pull your hair in that pony tail, you will accidentally motivate yourself to go out there and do it.
2. Time yourself
Tell yourself "I'm going to do this for 10 minutes, then I get a break," or "in 5 minutes, I'm going." Giving yourself a time limit allows you to psyche yourself up. If you say you're going to run for 10 minutes, you often times keep going for more without even realizing you had the motivation in you.
3. Tell yourself why
Sure, it would be easy never to leave my front door in a pair of running shoes, but I have to remind myself how great it feels when I'm done. I feel like I've accomplished something and I'm always in a better mood. Take the time to actually thing to yourself why you're doing what you do in the first place.