I wrote couple days ago about Nudge book I have read.. The main idea that people are full of flaws and they need help. It could be government assistance (like imposing taxes on harmful substances, or even banning them). Or it could be a society help. Good example of the last one is web site Stickk.com. As a default options you can make a commitment to site users to loose weight or to quit smocking.
As a nudge authors suggest Money. Because we hate loosing anything valuable and this fact can help you to stick your commitment. The most funny things is that you can decide who get you money if you fail. It could be charity organization, your foe or company you really hate!
How much money you bet is up to you, but they recommend to put something at stake, though. And finally you can invite referee who would monitor your progress. For example you can photo your scales and send results to some person (yes, lot of room to cheat =) ).
If you do not keen to spend entire evening in fighting with site you can ask you relative or friend to take your money if you cannot reach your goal. That was my was to loose couple extra pounds not long ago with my wife assistance, so I could prove that this is really works!