A personal letter in English can be addressed either to an old friend or to a new friend, who you don't know yet. The tone of your letter should be warm and show how you care about your friend. As this is an informal letter, you can work on the color and font of individual phrases that emphasize how you feel about your friend.
   
   What is appropriate/necessary to write in a letter to a friend in English?
     Tell your friend about something fun that has happened to you recently.
     Provide information about your hobbies and interests.
     Congratulate your friend with some event that is important for him/her.
     Tell your friend about an upcoming event or your plans.
     Share your family news.
     Ask your friend about his/her preferences (What's your favorite color? What sports do you do? Do you have any pets?
     Write about a new book you read or a movie you watched.
     Describe an interesting place that you have recently visited.
   Typically, a letter to a friend in English is focused on one main topic. At least, almost in any sample letters here you can find such a main topic.

The topics that are often found in a letter to a friend in English are the following:

Letters to a friend in English - How I spent the summer

Here you can find samples of letters to a friend about vacations, free-time activities, week-ends, picnics, all kinds of journeys and hiking trips, and the like. In these letters people share their vivid impressions and feelings.

Read more: Sample letters - How I spent the summer

Sample letters to a friend in English - About my family

When writing about their families, people usually tell friends about the family news and celebrations, joys and sorrows of their family.
This section presents sample letters in English about oneself, parents, brothers and sisters, other relatives, family habits and traditions, one’s house or apartment. Here you can find description of a best friend. There are the letters about family problems and other problems.

Read more: Sample letters - About my family

Sample letters - About the pets

Pets play an important role in life of many people, and we like telling our friends about our pet’s tricks and pranks.
Here you can find a general discussion of the role of pets in our life, as well as samples of letters about certain types of animals, like dogs, cats, horses, parrots, etc. There are also letters on our attitude to pets.

Read more: Sample letters - About the pets

Sample letters in English - Sports

Many people cannot imagine their life without sports. Some of them do sports, while others support their favorite team. Here are many letters to friends about different types of sports.
These sample letters in English are about sports in general and on individual kinds of sport like football, basketball, tennis, etc. About sports clubs, sports idols and their fans.

Read more: Sample letters in English: Sports

Sample letters in English - About my school

Young people write letters more often. Of course, issues related to education and school are present in their letters.
Here are the letters to a friend about school and related issues: exams, school subjects, school friends and teachers. A description of a school and a classroom. Here are sample letters about other academic institutions (higher education, etc.).

Read more:  Sample letters - About my school

About one’s preferences

Each person has their own preferences, someone likes collecting stamps, others prefer reading books of their favorite authors, and there are also people, who are fond of some natural sports. In this section you can also find sample of letters about music, movies, painters, museums, etc.

Read more: Sample letters - About one’s preferences

About cities and countries

Very often friends live in different cities and even countries, travel, visit places where they haven’t been before. Of course, they share their thoughts on the cities and countries where they live or where they have been.
Sample letters with references to countries, cities, and other places. All about geography.

Read more: Sample letters - About cities and countries

See also:

Sample letters to a friend in English

How I spent the summer

About my family

About the pets

About sports

About my school 

About cities and countries

About one’s preferences