I drew people lining up in front of the ticket booth to buy tickets. 

First, draw the horizon and set a vanishing point on it. Draw straight lines leading to the vanishing point, then draw guide lines on the floor based on those straight lines. 

 

After drawing other reference lines toward the vanishing point, draw the ticket booth. 

The reference lines we'll draw this time are the reference lines for drawing people.

Similarly, draw two reference lines pointing toward the previous vanishing point. The lower reference line is where the person's feet begin, and the upper line(same as the horizon) indicates their height. This line is the eye height of the person viewing this scene. 

I drew the first person. The feet start from the first reference line, and the head is higher than the second reference line. This means that this person is tall. 

I also drew a second person. Since his head height is similar to the second reference line, you can see that this person's height is similar to the height of the person viewing this scene. 

The third person is the second person's son.

Again, the feet start at the first reference. Since the head is lower than the second reference, we can see that this person is short.

The sketch is finished. I just colored it in briefly. 

People waiting in line in front of the ticket booth. 

Drawing people lining up in front of the ticket booth