If you are standing in a room, looking across to the far wall the lines where the floor, ceiling and side walls meet all appear to vanish at a single point ahead of you.
Every line that is parallel to these faces seems to vanish at that same point.
1. Start with a horizontal line for the horizon.
2. Pick the vanishing point and then draw the lines that are going away from you.
3. Put in the vertical lines.
4. Add any other details, making sure parallel lines go to the vanishing point.
5. Darken lines that you need.