1. Accept that your appetite and sleep patterns will no where near resemble normal for some weeks yet try to EAT and SLEEP as much as you can.  I made myself eat a banana every few hours, and rest during the day if I'd slept very badly. Take heart, my doctor assured me that you'd have to go for a long time with absolutely no food before you were in any serious danger and he added that as long as you're getting the minimum of 2 hours sleep a night your body can function.  So try not to worry about the disruption, it's normal, and doesn't last
2. Once you have actually broken up don’t ring, write or orchestrate accidental and unnecessary meetings. This will only jeopardize your self worth and dignity. Pleading/shouting/getting angry with them will only make them reluctant to even talk to you and it will also make you feel a lot worse. It won't make you feel better or change their mind.  Record your No Contact Agreement here
3. Don’t don’t don’t listen to pop music, (or country music as Kansasman pointed out).   Most pop songs are about soppy unrealistic never-ending Hollywood-esq love, spare yourself. (Click here for a list of the worst offenders).  After a few short days/weeks it might be helpful to listen to some angry, edifying music, my anthem for my break up was Britney Spears' ‘Stronger’
4. Avoid the use of alcohol/sleeping tablets/street drugs to try and dull the pain.  It won't work and you will be more inclined to do things you wouldn't when sober/straight, things that will make you feel awful when you straighten up. I actually avoided all alcohol until I was through the worst. There's also a high risk that you will form a stubborn addiction.
5. Grasp reality.  When various things make you crumble, whether it be a news reel about their favourite football team or a programme you enjoyed watching together remind yourself that the ex doesn't coach the football squad or write the programme!  There are millions of people supporting/watching etc.  This might sound peculiar but it helped me to ‘get a grip’.
6. Make a list of all the things that made you wanted to throttle the ex alive, or worse.  Often when we are the one left it can create a false sense of their worth, as if they must be a more desirable person then we, which is untrue. 
7. Get absorbed in a new book or project, like I did in building this community.  It provides an outlet for all that nervous energy. 
8. Pack up/burn/sell/donate to charity the gifts that your ex bought you and letters/cards that they sent you, basically remove anything that reminds you of them heavily, either temporarily or for good. You don't want to be finding pictures of them whilst rummaging in a drawer for last months bank statement.
9. Read children's books, you will find their simple stories and colourful pictures soothing.
10. Get crafty!  Have you ever experienced the peace and contentment that is Cross Stitching?  Try it.  It's a great way to occupy yourself.  There are numerous patterns to choose from, it's not just cute puppies and flowers anymore! 
11. Move your furniture around, buy fresh new bedding and paint a wall a new colour, this helps to re-claim your space as YOUR space.
12. Round up all the ex's belongings in your home and put them somewhere in a bag/box. Just keep them out of sight.  Don't worry about getting it to them, that's their job, and you'll only make it an excuse to see them otherwise, we've all thought about it!
13. Listen to talk based, current affairs radio stations.  The constant discussion on big issues will help to reinforce and remind you that, on the scale of things, your break up is a very momentary stage in your life.
14. Do The Cup Experiment
15. Keep a diary.  It illustrates how quickly we move through the process.  I found it vital to just sit and type type type.  When you get those overwhelming urges to e-mail/ring/IM your Ex, write it in your journal instead!  Also copy and paste helpful articles about surviving break ups (like this Survival Kit) from the WWW if it’s on your computer.
16. Pamper your body.  After a long bath you always feel an emotional boost. If you have been enjoying the occasional visit to the gym consider visiting for extra sessions.  It's a proven fact that exercise is a mood booster.
17. Look through the Archives here at the community to read lots of useful advice and encouragement. And check out Matt's Tips on How to Ease The Pain. 
18. If you do need to have contact in order to sort out matters of importance, such as access to any children, keep the dialogue polite and brief.  Resist the temptation to use the opportunity to bring up things to do with the relationship.  Also consider utilising a mutual friend in the dropping off/picking up of the kids until you feel more capable of seeing your ex without getting very upset and emotional
19. Allow yourself time to cry, it’s necessary, even you guys!  It will stop, sooner than you think.  Breaking up is a form of grieving, and there’s no shame in acknowledging the loss of the hopes that you held.
20. Talk to your friends, we’ve ALL been hurt and had relationships blow up in our faces.  I found my friends invaluable, my friends mean the world to me.  Talking helps us 'unfuzz' a lot of our thinking, and allows the dust to settle more swiftly.  
21. Try not to worry about the severity of your despair, it will pass.  If you’re concerned that you’re suffering over and above what you can cope with discuss your fears with your Doctor who will reassure you and discuss other resources you might not have considered such as counselling.

Click here to view and add your own suggestions for the Survival Kit