Since contractions are not required in English, it is more important to be able to interpret them than to produce them.  I wonder whether it would be better to give this lesson by presenting the contractions as almost-words, some with multiple meanings.  For example:

'd - would / had

I'd put it there - I would put it there / I had put it there

He'd left it behind - He had left it behind

I'd trust you if you smiled more - I would trust you if you smiled more

'll - will

I'll try - I will try

They'll start tomorrow - they will start tomorrow

's - is / has

Don't confuse this with the possessive marker 's!

Sam's a great friend - He is a great friend

Sam's found something - He has found something

Sam's dog is grey - (Sam has a dog, which is grey)