I use the "foot in the door" method. For me I call it -- "just run ONE mile on the treadmill". As you said, most times I go more than that. But not always.... sometimes it feels like a chore all the way through it and I stop after a mile. But the difference between just that one mile versus absolutely nothing is HUGE!
I also agree with the poster above who said that picking a race, especially one that a friend is doing, can help give you a boost. I did that in Nov. and Feb -- guess now that it is April, maybe I should try to pick another one.