It's not complicated: First, you draw the interior of a room. Second, you draw tables. Next, you populate the room with people, and then you draw the plates of food. The sum of these parts may look complex, but taken in individual steps, one at a time, drawing the interior of a restaurant simply requires patience and some basic drawing skills.
Drawing the Room
In the center of the page, draw a rectangle wider than it is tall, 5 inches by 7 inches. This is the back wall of the room.
Use your ruler to draw a very light X across the wall. This X will spread from corner to corner. The very center of the X will be the vanishing point.
Erase the X, but leave the vanishing point.
Place one end of the ruler on the vanishing point, and then pivot the ruler on the vanishing point until it forms a straight line to the top right corner of the back wall. Leave the ruler in place and draw a line along the ruler from the top right corner of the back wall and out to the edge of the paper. This line represents the edge of the room where the ceiling meets the right wall.
Pivot the ruler until it points from the vanishing point to the lower right corner of the back wall. Draw a line along the edge of the ruler that points from the lower right corner of the back wall to the edge of the paper. This line represents the edge of the floor and the edge of the right wall.
Pivot the ruler again until it forms a line from the vanishing point to the upper left corner of the back wall. Draw a line along the ruler from the upper left corner of the back wall to the edge of the paper.
Pivot the ruler again until it forms a line from the vanishing point to the lower left corner of the back wall. Draw a line along the ruler from the lower left corner of the back wall to the edge of the paper.
Draw a series of thin horizontal ovals two fifths up the side of the back wall. These ovals represent the tops of the tables at the back of the room.
Draw a vertical line from the far left corner of the tables down to the floor. Draw another vertical line from the right corners of the table down to nearly the floor. These vertical lines represent the right- and left-hand side of the table cloths.
Connect the two vertical lines hanging down from each table top with a wavy line. The wavy line should curve in a way that mimics the curve of the table. This is the bottom of the table cloth.
Repeat Steps 1 through 3 for a row of tables farther down the page. These tables will be the same as the the tables you just drew, except the ovals will be slightly wider. More of the table tops will be visible as the tables move closer to the front of the room.
Repeat Step 4 for another row of tables, this time allowing the tables to meet the bottom edge of the paper.
Drawing Chairs and People
On either side of each table, draw a vertical oval floating in the air. These ovals are the heads of the people sitting at the tables.
Draw slender necks down from the heads then expand the necks where they meet the shoulders.
Draw the edges of the shoulders curving down into the arms and past the edges of the table.
At left and right corners of the shoulders, draw the left and right corners of the chairs.
Draw several oval-shaped plates on the tables.
Beside each plate, draw a cylinder sitting on the table (these are the glasses).
On the back wall, draw several square pictures in picture frames.
Erase any unnecessary marks, such as the edges of the back wall that can be seen "through" the tables.
Although this article has declined to describe how to add details to the people, this may be done. Described in this article are the bare-bones of a restaurant interior. You can choose what shall be added from here.