If you want to do this with goals that involve gradual effort rather than achieving a single success or avoiding a single failure, you should do your commitment contracts with Beeminder. Examples: writing a blog post once a week, learning 30 Chinese words a day, losing 1lb every 2 weeks, working 60 hours a week on your startup. If you have a goal and you are worried about not having enough motivation to do it, there are very few valid excuses not to use a commitment contract to max out your motivation (which not only ensures success, but also means you have more fun).

Love it. Learning French on Memrise; 200 pushups to my partner for every day I skip.

creepy---I'm paying my friend right now $50 to keep me on track to do paleo. Been doing it for a month. The only thing that's ever worked for me.

I was following a link to to go Sebastian's post "In college? Starting a business? Learn accounting and sales." and instead I ended up here. What gives?

I did this with Stickk.com. You make a contract with their site and give them your credit card number before you begin your goal. You also use a referee such as a friend to verify whether you're doing it, so you can't lie. With stick you pick "Anti-charities"--for example, if you're an industrial technology loving capitalist like me, you choose to donate to an environmental group for each week you fail in practicing your habit. The good thing about it is that if you fail one week, things aren't all over. You have to continue the next week or you'll get penalized again. I got a lot of Korean studying done in conjunction with that site.

tyler cowan's version of this is, "if i don't (goal x) i'll send $100 to the KKK."

i personally don't use this strategy because i know sometimes i fail, it would lead me to focus on too easy challenges, because i fear commitment.
your recent post about just do it did get me off my ass and i got a few things done i'd been putting off.

Thanks for the great post... I just promoted it to the front page. 

The first time I did pickup, I would hand the keys to my Mercedes to a friend and tell him the car was his if I didn't do X approaches. It would shift my whole mindset away from excuses, because no excuse would get my car back if I didn't succeed.