When a person is bored, they whole body is telling you. So if you are trying to persuade them, don't bother (unless you are trying to bore them into submission).
Language of boredom
A ready body is poised for action.
Distraction
A bored person looks anywhere but at the person who is talking to them. They find other things to do, from doodling to talking with others to staring around the room. They may also keep looking at their watch or a wall clock.
Repetition
Bored people often repeat actions such as tapping toes, swinging feet or drumming fingers. The repetition may escalate as they try to signal their boredom.
Tiredness
A person who feels that they are unable to act to relieve their boredom may show signs of tiredness. They may yawn and their whole body may sag as they slouch down in their seat, lean against a wall or just sag where they are standing. Their face may also show a distinct lack of interest and appear blank.
Reasons for boredom
Lack of interest
If the person is not interested in their surroundings or what is going on, then they may become bored. The disinterest may also be feigned if they do not want you to see that they are interested. Watch for leaking signs of readiness in these cases.
Readiness
A bored person may actually be ready for the actions you want, such as closing a sale. Sales people are known to keep on the sales patter long after the customer is ready to sign on the dotted line.