3.  The 180 degree rule

Above is a diagram which shows the 180 degree rule. 

It is a rule that is vital when filming a discussion between two people. the rule states that two characters in a scene should always have the same left/right relationship to each other. however if this rule is not followed and is broken, for example filming on the opposite side, it disrupts the scene and confuses the audience as it will appear as if the two characters have swapped sides and in some cases can look as if one character is talking to themselves. Therefore we shall stick to this technique when filming, to prevent the audience from getting confused.