Trainwreck relationship disasters have the same basic shape as any other catastrophic events -- dazed, wounded, homeless survivors, shattered dishes, orphaned pets. Here are some basic rules to follow when and if the world comes crashing down
Note: These rules are for the dumpee, not the dumper. Some more sympathetic soul might want to take that on.

1. Don't Drink!
I know it seems totally counter to instinct -- at the time it seems to make perfect sense to walk the streets in a bathrobe working your way through a bottle of Creme de Menthe. Believe it or not, the drunken behaviour you perpetrate now will make it that much more difficult to re-insert yourself into polite society later. Plus, you may attempt a drunken reconciliation with your dearly departed, which is, as Martha Stewart says, "a bad thing."

2. Get the Pets
After your friends, nothing will provide you with more solace. Swipe them off the porch if you have to.

3. Get the Word Out
Almost as soon as s/he drops the bomb, a propaganda scramble begins. Your dearly departed will try to spread a syrup-y tale of bittersweet loss ("We just decided it wasn't working out...") to cast into doubt your story of seething betrayal ("He/She was engaged in a protracted and torrid affair with your best friend which you only discovered as the result of misdirected email"). So get your story out there. Make sure everyone knows it -- his/her parents, friends, and small children on the street, who will follow the offender and pelt him/her with stones.

4. Circle The Wagons
Even if this thing came from out of the blue, there is a very short window of time before your nouveau-ex starts making the rounds of your shared friends, making sure that in the Friend Division, they stick with him/her and not with you. Don't let it happen. You'll need them later to help you move, provide much-needed escape cash (see next), and entertain you at dinner parties in your new single life. They are vital to your rehabilitation as a whole person, so make sure you follow Step 3 with them especially.

5. Get Outta Town
A very good idea. You're going to be a leper for a little while, even with your friends. They will tiptoe around, workmates will whisper, your parents will call to say "But we thought s/he was so nice!". Forget it. Borrow a whack of cash from the friends in Step 4 (This is very important). Go at least 500 miles away, to the well-appointed home of a friend who barely liked your ex in the first place. Get on a plane if at all possible. Ideally, the locals should have accents (and not New Jersey accents). Go out. Buy cool clothes. Get a fabulous haircut. Flirt with aforementioned accented locals. Read good books and cook good food. Return a new person.

6. New Digs
Find a totally cool home or a home-with-potential that can be turned into a cool home. Difficult, but very important. If you live in a hole after the breakup, he/she has won -- your spirit will be broken and your new haircut will seem like a hollow gesture.