Simple:
* The child's imitation of his father's walk was hilarious.
* The diamond ring was actually a cheap imitation.
More complex:
* Through imitation, young birds learn the songs specific to their species.
* The artist's imitation of the famous painter's style was so good it was almost indistinguishable from the original.
* The actor's imitation of the politician's speech patterns was spot-on.
* The imitation leather jacket was a good deal for the price.
Figurative:
* The new restaurant was an imitation of the popular one down the street, right down to the menu.
* His attempts at writing poetry were just an imitation of the real thing.
The best way to use "imitation" will depend on the specific context of your sentence.