Draw a freebody diagram showing the forces acting on a box sat on a table

The first thing to note is that the book is sat on the table, so it is stationary. From newtons laws, we know it must have 0 total force acting on it. Every object on the earth feels a force downwards due to gravity, so we draw an arrow downwards from the centre of the book. Since the object is stationary, we need a second force to oppose gravity. To keep the object still the force must be equal in size and in the opposite direction. We draw this force as an arrow the same length as the first but directly up from the centre of the book. This completes the diagram as no other forces are acting on it.