Pour commencer la description, tu devras déjà te poser quelques questions dans un certain ordre (du plus évident au moins évident, du plus général au plus précis). Voici une liste de questions que tu devras te poser et les réponses que tu peux y apporter en prenant l'exemple de la photo ci-dessus. 

1) What type of document is it ?

Ÿ       a picture

Ÿ        a photograph

Ÿ       a cartoon                                 

Ÿ       a painting 

The document is a photography

2) Where was the photograph taken ?

The photography was taken in New York, on Broadway Avenue. 

Si tu ne connais pas la ville, tu peux utiliser des astuces en restant vague : 
(Tu peux savoir que c'est une ville américaine si tu fais bien attention aux détails : les taxis sont jaunes, il y a des grands immeubles...)

- This photograph was taken in a big city
- This photograph was taken in an American city
- It shows an urban landscape
- I can see a big city

3) Who can you see in the picture ?

Ÿ       a man

Ÿ       a woman

Ÿ        a girl

Ÿ        a boy 

I can see many people walking on Broadway avenue : lots of men and women, girls and boys. There are people crossing the street in the foreground and in the bottom left hand corner and in the bottom right hand corner. 

4) What can you see in the picture?

I can see big buildings in the top-right-hand corner and in the top-left-hand corner and also in the background. These buildings are called skyscrapers and big building in the background and in the right and left hand corners; these buildings are called skyscrapers. I have seen many skyscrapers in movies that took place in American cities, such as in CSI (les experts)

5) What are they doing?

  
Some people are walking on the street, and others are crossing the street.

Pour finir tu fais un résumé, en utilisant les informations que tu as trouvées et en reliant le plus possible les phrases entre elles.

Ex : The document is a photograph. It was taken in a big city. I can see New York. It is an American City.

Cette phrase va devenir : 

This document is a photograph which was taken in New York, a big American city. 

Tu peux dire comment tu es arrivé à deviner que c'était une ville américaine en disant  : 

I know that it is an American city because there are yellow taxis in the foreground and big buildings in the background and in the right and left hand corners; these buildings are called skyscrapers. I have seen many skyscrapers in movies that took place in American cities, such as in CSI (les experts)

To describe a picture with a more refined vocabulary, click on this link
http://www.english-for-techies.net/mainstream%20vocabulary/photography.htm