to take time by the forelock
to embrace the opportunity
to improve the occasion
to improve the opportunity
to make use of the occasion
to profit of an opportunity
to take advantage of the opportunity
to use one's opportunities
to play on sy's credulity
to play upon sy's credulity
to lay hold of sy's weakness
to practise upon sy's weakness
to trade on sy's ignorance
to trade upon sy's ignorance
to make one's money go far