First, make it public. The more friends (or enemies) know you want to quit smoking or get a new job, the better. Peer pressure can be a good thing.

Secondly it helps to have a financial incentive. If you know you will lose a hundred dollars when you light that cigarette, will you still do it?

And then there are no-brainers like the need to be specific and have a definite date in mind.

Since this blog writes about internet it makes sense to mention that myself and a few friends took all of the above and created http://www.pledgehammer.com on our free time. Not only does it help to make and keep resolutions, it also helps charities raise more money via donations. Would be great to get more people to try it out and hear your feedback.