Mystery Is Easy - How to Crack Agatha Christie?

I just finished reading 'Murder Is Easy' by Agatha Christie, the queen of mystery. Here the lead of novel meets an old woman on a London bound train and gets to know about mysterious deaths taking place in a desolate village, not far from London. The old lady mentions to this retired police officer, that she is going to report to the Scotland Yard the murders and the suspect according to her. But, the police officer reads in next day's newspaper that the old lady has been knocked down by some vehicle in London. Determined to see to this affair, the lead goes to village, falls in love with a lady besides trying to unfold the murder mysteries. Regular stuff.
I actually had zeroed down on 3 persons in novel as possible murderers when I was somewhere in the middle of novel. And bravo! Here are the actual results - First one the pompous Lord is closely related to the murderer; Second, the lady - in whose case I failed - is not the murderer, but in fact becomes muse of the lead; the third one - the old lady once engaged to the Lord is the actual murderer.
Now, here is my formula of how to crack murder mysteries before Agatha Christie does that on
last/secondlast/thirdlast page.
It is quite simple. Just remember following facts about the murder mystery - 

• The murderers appear at the earliest stages of novel.
  
• They are delved upon to lesser extent inspite of being lead players
• Those, whose eccentricities, murderous sides are exposed again and again in the novel are NOT murderers. Stay away from them (and pray the hero doesn't waste much time on them)
• The investigators are silly fellows - ignornig obvious facts. You don't be silly.

• Inspite of this, if you fail, then don't be sad. The mystery novel is meant for that.

How about writing a mystery novel, like Agatha Christie? More than writing skills, it needs some mathematical, analytical mind.

1. Write a simplest murder story with all facts.
   
2. Now you have characters - facts - character info; one murderer; one investigator
   
3. Wipe down character info as much as possible, without making the character look suspicious by lack of info about him/her
   
4. Now, make one more pseudo-murderer. He/she will come handy to create twists
   
5. Your murder mystery is ready now. Just don’t tell the readers some facts here and there. Create small twists throughout [twist=suspect somebody-show that he is not the real one].
   
6. Finally, twist before main exposure is extremely important for the ‘Orgasm’ at the climax. Here you make the reader believe that the pseudo-murderer is the real one. Obviously, you make reader think like that by making your investigator think like that. Readers will read it and draw desired conclusions.
   

Here is the graph -