Could of, would of, should of: these common misunderstandings stem from a failure to realise that, in speech, the contractions ‘would’ve, could’ve and should’ve’ sound as though ‘of’ is used. But, these expressions are actually contractions of the phrases, ‘would have, could have and should have’. Therefore, the correct usage is ‘would’ve, could’ve and should’ve’.
If you have difficulty in remembering this, simply see whether the sentence would sound correct if you substituted ‘would have’ for the contraction. There is no linguistic or grammatical case in which ‘would of, could of or should of’ is correct, and using it will make you appear ignorant.
‘If I’d known I could’ve come over sooner, I would’ve.’
4 July riots occurred in Toxteth 30 years ago, with the flames of destruction fanned by a hot summer.