Planning on running a Marathon? , never put yourself in this position

Well, any site on the web or any professional long-distance runner has one advice for the amateur runner who wants to experience the out of the world journey
of completing a marathon. Start preparing three to four months before the race. Have a schedule set up for each week with designated days for rest each week.
Do cross training, i.e do something else than running on atleast one day of the week.Keep increasing the distances you run every week.
Follow a low-high-low pattern of running distances.

For Example:
Week 1:
Monday : 5 kms
Tuesday : 6 kms
Wednesday : 7kms
Thursday:Rest
Friday :8 kms
Saturday :12 kms
Sunday: Rest
Week 2:
Monday : 7kms
Tuesday : 8 kms
......and so on.

Well these are the do's of preparing for a marathon.
Can someone give the dont's??
If there is some way to go about doing normal things in a crazy way, you bet there will be a person crazy enough in this world to do it.
And to do the honours this time, we have ( with utmost surprise and shock ) me !!!

Here goes the What Nots :

1.) Never get up on a day and suddenly realise that you had made a credit-card transaction some months ago to pay for the registration fees
of a marathon which is just a few weeks away.

2.) The worst possible scenario at this point would be to realise that you have not run a kilometer straight in the last 6 months.

3.) If that was not enough , there was nothing done in teh past few months that could be mistaken as cross-training , no activity that could atleast strength your muscles or lungs or heart or brain(do you think just legs are enough???)

4.) The worst can become worse when you realise that the reason you did not run for the past 6 months was that you carry an injury in the area around your left knee from your last long distance run.

5.) If the situation isn't already bad enough , the first time you take your legs out to try them on, you discover pain shooting along the path from the back of your left knee to your thigh.

6.) The speed you can run is atleast 3kms/hr below your average speed.

7.) You have no running partner , to go along with you over such a long distance (atleast there should be someone nearby , handy enough to resuscitate you ).

8.) You know of nobody who has done the marathon in the position that you are in.

9.) You realise going by your logic and the reality of pain that this cannot be done.