Rules for Writing Formal Letters in English

Rules for Writing Formal Letters in English 
In English there are a number of conventions that should be used when writing a formal or business letter. Furthermore, you try to write as simply and as clearly as possible, and not to make the letter longer than necessary. Remember not to use informal language like contractions.
Addresses:
1) Your AddressThe return address should be written in the top right-hand corner of the letter.
2) The Address of the person you are writing toThe inside address should be written on the left, starting below your address.
Date:
Different people put the date on different sides of the page. You can write this on the right or the left on the line after the address you are writing to. Write the month as a word.
Salutation or greeting: 
1) Dear Sir or Madam,If you do not know the name of the person you are writing to, use this. It is always advisable to try to find out a name. 
2) Dear Mr Jenkins,If you know the name, use the title (Mr, Mrs, Miss or Ms, Dr, etc.) and the surname only. If you are writing to a woman and do not know if she uses Mrs or Miss, you can use Ms, which is for married and single women.
Ending a letter:
1) Yours faithfullyIf you do not know the name of the person, end the letter this way.
2) Yours sincerelyIf you know the name of the person, end the letter this way.
3) Your signatureSign your name, then print it underneath the signature. If you think the person you are writing to might not know whether you are male of female, put you title in brackets after your name. 
Content of a Formal Letter
First paragraphThe first paragraph should be short and state the purpose of the letter- to make an enquiry, complain, request something, etc.
The paragraph or paragraphs in the middle of the letter should contain the relevant information behind the writing of the letter. Most letters in English are not very long, so keep the information to the essentials and concentrate on organising it in a clear and logical manner rather than expanding too much. 
Last Paragraph The last paragraph of a formal letter should state what action you expect the recipient to take- to refund, send you information, etc. 
Abbreviations Used in Letter Writing
The following abbreviations are widely used in letters:
asap = as soon as possible
cc = carbon copy (when you send a copy of a letter to more than one person, you use this abbreviation to let them know)
enc. = enclosure (when you include other papers with your letter)
pp = per procurationem (A Latin phrase meaning that you are signing the letter on somebody else's behalf; if they are not there to sign it themselves, etc)
ps = postscript (when you want to add something after you've finished and signed it)
pto (informal) = please turn over (to make sure that the other person knows the letter continues on the other side of the page)
RSVP = please reply
Outline: A Covering Letter
A covering letter is the one that accompanies your CV when you are applying for a job. Here is a fairly conventional plan for the layout of the paragraphs.
Opening ParagraphBriefly identify yourself and the position you are applying for. Add how you found out about the vacancy.
Paragraph 2Give the reasons why you are interested in working for the company and why you wish to be considered for that particular post. State your relevant qualifications and experience, as well as your personal qualities that make you a suitable candidate.
Paragraph 3Inform them that you have enclosed your current CV and add any further information that you think could help your case.
Closing ParagraphGive your availability for interview, thank them for their consideration, restate your interest and close the letter.
Outline: A Letter of Enquiry
A letter of enquiry is when you are approaching a company speculatively, that is you are making an approach without their having advertised or announced a vacancy.
Opening ParagraphIntroduce yourself briefly and give your reason for writing. Let them know of the kind of position you are seeking, why you are interested and how you heard about them.
Paragraph 2Show why their company in particular interests you, mention your qualifications and experience along with any further details that might make them interested in seeing you.
Paragraph 3Refer to your enclosed CV and draw their attention to any particularly important points you would like them to focus on in it.
Closing ParagraphThank them, explain your availability for interview and restate your enthusiasm for their company and desire to be considered for posts that might as yet be unavailable.
Sample letter 1: Covering letter
12, Kenmore RoadLittletownLT12 9BH
1st December 2001Mr G. SandsFitness FirstLake RoadLittletownLT1 5MXDear Mr SandsRe: Fitness Instructor FF/32I am writing to apply for the job of Fitness Instructor, as advertised in Thursday's Courant. This is an ideal job for me given my enthusiasm for sport, my related experience and qualifications.Sport and fitness training have always been important to me, which is why I chose to take a BTEC Diploma in Sports Science. I obtained distinctions in the Sports Anatomy & Physiology and Sports Injuries modules last year and am confident that I will get similar marks in Exercise Physiology, Mechanics of Sport and Sports Supervision & Management this year. I am a confident user of Microsoft Office 2000 and have worked extensively with Fitness Publisher, a program for analysing fitness.As you can see from my CV, I've taken the opportunity to gain extra qualifications that were on offer at college, which has helped me get part-time work as a pool attendant. I'm called on to provide cover during busy times so am used to working irregular hours at short notice. I've also run a lunchtime aerobics class at college since the start of this year.I finish college in six weeks and am keen to find a job rather than carry on with further full-time study. I could start any part time work or training sooner as many of my classes are finishing and most of my assignments are done. I look forward to hearing from you.Yours sincerely
Louise Longford
Sample letter 2: Business letter
Whitcomb Polytechnic20-30 Newcastle RoadWhitcombeTyne and WearWT5 4AH 11 October 1997
The General Manager Fukuoka Motors (UK) LtdPO Box 137York RoadLoughtonDurhamLT3 5HD
Dear Sir
I understand from my colleague, Professor William Jones, who visited your Loughton plant last month, that you sometimes allow groups of students to tour the factory and see for themselves how Japanese production techniques operate in a European environment. Professor Jones himself was most impressed by his own visit, and recommended that I write to you.
Would it be possible for a group of 20 Business Studies students - male and female, aged between 18 and 22 - from Whitcomb Polytechnic to visit you before the end of this term, which is on the 21 December? I realise that you must receive many requests for such visits, and that the time available may already be booked up. If it is not, and you are able to see us, I should be most grateful if you could suggest a date and let me know of any normal conditions you lay down for visits of this kind.
I look forward to hearing from you.
Yours faithfully
B Farrant (Dr)Senior Lecturer