METHOD
Choose a photograph that appeals to you. I don't think there is anything wrong with using photographs to help you with your work because you are learning a specific skill while doing it. As you know, things get smaller as they get further away. They also get less distinct. In other words, there is a sharper contrast between things in teh foreground of your picture and those in the distance. So ensure that you paint strong contrasting shapes in the front and make things softer at the back. Your photograph should help you sto see this.
Remember to use the paint thickly, creating light colours by mixing with white. A good natural green can be made by mixing yellow with black.
RESULTS
The group werer very please with their pictures. Look at your picture from a distance and you will see that your work is now becoming more three dimensional and using all the space in the picture effectively.