When a person pretends to do something or lies they do it excessively.
A person pretending to look at something, will do it so excessively it is like their eyes are popping out of their sockets. (Constantine Stanislavsky)
A person pretending to move will move with such exaggerated movements it does not look real.
A person who is lying, will talk about their story excessively, because they are trying to prove it to be true. This is a good way to see that someone is lying, they talk excessively talk about their story, in such detail and for such a long time. If it were true, they would feel no need to do this, or even bring it up and go over it all.
So the answer with acting is not to do it an a way that proves or on purpose shows it to anyone.
The only way to really do it is to do it for real. for example look at the item for real and do things for real. When doing something for show, it just looks silly.