An informal letter is a personal letter written to relatives, friends, or business partners with whom one has a personal relationship. An informal English letter includes an address, date, opening, body, closing, and signature. When writing the body, one should use friendly language and social niceties while adjusting the tone based on the recipient. The opening can be as simple as "Hi [name]" with a comma and should state the reason for writing. Example closing sentences are "I hope to hear from you soon" or "Send my love to...". Signatures for informal letters can be short like "Best wishes" or "Love".

1. An introduction

2. What is an informal letter?
What is an Informal English letter?
An informal letter is a letter that is written in a
personal fashion. You can write an informal English
letters to relatives or friends, but also to other people
with whom you have a personal/informal way of
interacting. This can also be with Business partners
that address you in a personal and friendly manner. In
a lot of countries there are of course different ways of
doing this. Here only the English and the American
way is addressed

3. What elements does the letter
include?
Address
Date
Opening
Text / Body / Content
Closing / End
Signature

4. Text / Body or Content
When writing an informal letter in English you should
use personal/friendly language. However, it remains
important to adjust your use of language to the person
you are writing to. A good way of assessing how you
should write is thinking about how you would interact
with each other in real life. Another thing, the English
and the Americans are fond of exchanging some social
niceties. So they like asking a few polite questions etc.
They are in general not so direct as most Europeans.

5. In the first paragraph of your body you state your
reason of writing. In the second and following
paragraphs you say what you have promised to say in
the first paragraph. And in the final paragraphs you
make some concluding remarks.

6. Opening of an informal letter in
English
How to address someone in English?
This is fairly straight forward. It is usually not of the
same importance as with a business or formal letter, but
it still is relevant. There are a few things that you should
know about how to address someone properly in an
informal letter. First of all, in England there is not .
behind Mr., but in American letters there is. Secondly,
you should know that women are addressed with Mrs.
when they are married, and with Ms. when they are not.

7. Examples of how to open an
informal letter in English
This heavily depends on how well you know the person
in question. You should carefully consider your
relationship with the person concerned. You could
simply say: Hi Richard, but it is always safer to just
say Dear Richard,. Never forget the comma!

8. Opening Sentences for an
informal letter in English
Examples of opening sentences
Opening sentences of an Informal letter should be casual.
Not so stiff as in Business letters. For examples of more
formal opening sentences you should check out my
business letter article.
How are you?
How have you been?
How is life treating you?
How are the kids?
I hope you are doing well
I hope you, Mike and the kids are having a great time in ...

9. Ending an informal letter in
English
Examples of closing sentences - how to end an informal
letter in English?
I am looking forward to seeing you,
I can't wait to see you soon,
I can't wait to hear from you,
I am looking forward to hearing from you,
I hope to be hearing from you soon,
See you soon,
Send my love to ..
I hope you are doing well,
Give my regards to..,

10. Signature
Here you can be pretty free in your choice of ending
your letter. Here are some examples of a signature for
an informal letter in English
Best wishes,
Kind regards,
Best regards,
Lots of love,
Love,

11. Source
http://markinternational.hubpages.com/hub/Examples-of