When Yosef Hatzadik was about to be Nichshal with the wife of Potifar, it was the image of his father's face that woke him up and stopped him. The Gemara talks about those who would make a Shevua to stop themselves from doing something wrong. We all know the famous story of Rav Amram and his using Boosha to stop himself.
My advice to you would be: Think good and hard before you are in front of the computer about something that is most precious to you. For a Bochur that might be his potential Shidduchim, or losing the respect of his closest friends and Rebeiim, while for a married guy it may be his wife or children. Then, think of a way to set yourself up a reminder that will instantly bring that thing back in front of your eyes and on your mind when you need it most. Lastly, put that thing somewhere near enough to your self while at the computer, or near the computer itself, so it will be ready and available in case of emergency.
Just as an example: As a married guy with wonderful beautiful Heilige children, there is nothing in the world that I would care to lose more than them. So I paid about $10 and I got myself a mouse pad specially made with a picture of my smiling children on it. When I am vulnerable, I use that mouse pad to remind me of why I don't want to do this.
Remember, anything you do can work, if you tailor-make it to yourself while in the proper state of mind. It is very subjective.