You need:
Informal language, including phrasal verbs, informal vocabulary ("I guess you loved the pics"), contractions, question tags.
An informal letter or email is usually between people who know each other fairly well. In addition to giving news, they are often used to request information, congratulate people, give advice and ask questions. There are a lot of similarities between informal letters and conversation. Informal letters ask a lot of questions, show interest and enthusiasm, and imagine a lot of shared information.
you can also start with Hi (and the person's name)
EXAMPLE: Dear Ben, or Hi Ben,
Openings
Useful phrases for the opening
Other useful phrases
Referring to news
Giving news
Apologies
Requests
Thank you / Congratulations / Good Luck
Making suggestions and recommendations
The end of your letter is as important as the beginning.
You can:
References: