Question

format of english letter writing 

Answer 1

formal or informal?
ok I will write both.
FORMAL-
1) Your Address 
Your address should be displayed in the top right-hand section. This will enable the person that you are writing to, to reply.2) The Address of the person you are writing to
This address should be displayed beneath your address on the left-hand side, remember to include the name of the person that you are writing to (if known).Date:This should be displayed on the right-hand side of the page on the line beneath your address and should be written in full format:e.g. 1st January 2001Salutation & Greeting:1) Dear Sirs,
If you do not know the name of the person that you are writing to, use the greeting "Dear Sirs,". In some circumstances it is useful to find a name, especially if you are making a request as this will show that you have done your homework and you are more likely to receive a response.2) Dear Mr Jones, 
If you know the name, use one of the following titles:Mr - for a male
Mrs - for a married female
Miss - for an unmarried female 
Ms - for a female whose status is unknown or would prefer to remain anonymous 
Dr - for a person with the status of a doctorThis should be followed by the surname only (not the first name).Concluding:1) Yours faithfully,
If you do not know the name of the person, conclude with "Yours faithfully,".2) Yours sincerely,
If you know the name of the person, conclude with "Yours sincerely,".3) Your signature
Sign your name, then print it underneath the signature. If it is potentially unclear what your title would be then include this in brackets next to your printed name.

Answer 2

FORMAT OF "INFORMAL LETTER":
1.) Sender's Address - it starts with the with the smallest possible detail to the large one. Eg:
 house no. 20, 1st bye lane,
Barabazar, Kolkata - 700007
West Bengal
2.) Date - it should be written as 16th Sept, 2015.
3.) Salutation - Dear dad/mom/grandfather/grandmother...etc
4.) Body of the letter - it should be in 3-4 paragraphs.
5.) Subscription - your loving son/daughter, your affectionately, yours faithfully...etc
6.) Signature - just write your name or the character you are supposedly writing.

FORMAT OF "FORMAL LETTER":
1.) Sender's Address - it starts with the with the smallest possible detail to the large one. Eg:
house no. 20, 1st bye lane,
Barabazar, Kolkata - 700007
West Bengal
2.) Address of the addressee - address of  the person you are sending to. Eg:
To
The Princpal
Delhi Public School,
Kaifi Azmi Marg, Sector 12,
RamaKrishna Puram, New Delhi,
Delhi 110022
3.) Date - it should be written as 16th Sept, 2015.
4.) Salutation - Dear ma'am/sir...etc
5.) Subject - it should be precise and direct. Eg: correction of name in school enrolment
6.)  Body of the letter - it should be in 3-4 paragraphs.*
7.) Thanking you - just this no need to add more to it.
8.) Subscription - yours sincerely, yours truly...etc
9.) Signature - just write your name or the character you are supposedly writing.
* if its a letter to the editor, follow the format of formal letter. just start your first line of the first paragraph as: "Through the esteem column of your newspaper, i would like to.....(draw the attention of the concern authority regarding/express my views on)..etc

EVERY THING IS ON THE LEFT MARGINS
I HOPE THIS IS HELPFUL TO YOU.