So, the nature of congratulatory letters can be, depending on the situation:

- serious (colleagues, boss);
- age (appeal to younger, same age, elder);
- easy humorous.
- etc.
On the Day of birth, as a rule, invite friends, relatives, colleagues or partners. If you are a friend or relative of the hero of the occasion, take advantage of the fact that you know him well. Mention in the greetings of his unusual or rare Hobbies, remember with good humor interesting or dangerous situation with your joint participation.
Of course, we should not forget about who participates at the festival. For example, if you read the story of the adventures of the birthday boy in the Sorority house, in the company of old friends it will be a real Jolly, but if you will be attending by his parents, is unlikely to be a good option congratulations. In this case you need to write seriously about what you have with the birthday boy before he you like. Of course, at the end of his speech, wish him all the best, from the heart, avoiding the standard phrases like "on this auspicious day..." or similar.
Original will you do, if you write a funny monologue on behalf of your friend, and then read it in front of all the guests and ourselves. It is desirable to include in the narrative the facts that he knows most of the guests to be interesting and it was clear to all. For example, make one of the characters in your story cat birthday, which in size is not inferior to the average dog, about his washing machine which is constantly breaking down, his love for computers. Try not to overreact – even if the humor is good and easy.
If you are a colleague of the birthday boy or partner, in greeting, and in General the communication is not too familiar. You can use his address to the hero of the festivities formulaic phrases like "I Congratulate you, dear Ivan Ivanovich, I wish you happiness in your personal life and success in work". Just don't overload the text templates, and need something different to write also. Can be limited to the classics of the genre – a line from a story Milne about Winnie the Pooh, namely "happy birthday, I wish you happiness in personal life! Fluff".