Don't Give Up Giving Up
Firstly, try and be as realistic as you can about your resolutions. Don't go for impossible ones, such as "winning the lottery" but rather consider better money management as a realistic goal if this is an area you want to improve on.
Review the different areas in your life and think about what is working as well as what isn't. Instead of picking the same old resolutions that you can never seem to keep such as giving up smoking, choose an area that you know needs improvement rather than a radical change. And don't make too many resolutions - you'll find yourself overwhelmed and less likely to stick with them all.
Diet and healthy eating are resolutions made by millions every January. A mental method known as "framing" helps you make better day-to-day decisions by putting things in proper perspective. Try telling yourself that just for today, just eating one biscuit won't be all that bad. But then tell yourself that if you keep eating like this, you'll be eating more than ten stone of biscuits during the year, and by the end of the year, you'll be almost a stone heavier as a result.
As you think about eating that one biscuit, put an image in your mind of what you'll look like after eating 365 of the things -- it'll quickly put you off talking yourself into "just one."
Focus one thing at a time
Rather than trying to make several large changes all at once, such as trying to lose weight, giving up smoking, and exercising regularly, break the changes down into smaller lots and focus on one single resolution at a time. Your focus and energies won't be spread too thinly this way and your chances of success will greatly increase.
Create a solid support network
Tell a friend or loved one whom you trust about your resolution. They will keep you focused on your goal and make you less likely to give in as you'll feel as though you're letting them down.
Look at national support groups too such as those that provide support with giving up smoking, get advice from your GP or get a personal trainer to help you stick with workout goals. The more help you have, the better, and no one will think less of you for needing a little help every now and then!