Here is a nice exercise you can do to remind you of how you break down a photo image into various sized blocks.

Start off by dividing the image up into the largest divisions of space, draw lightly with a hard graphite pencil. When you are happy that you have an accurate representation of the largest blocks firm up the lines with a coloured pen. Do the same for the medium blocks with pencil first then with a different coloured pen. That’s the drawing exercise finished - the aim of the exercise is to help develop your observational skills and your accuracy in judging the size, shape and position of objects within a picture frame. It is important to develop this skill first before going into details and values and eventually colour.