1 to avail oneself of

2 to take advantage of

1 as soon as possible

2 at the first opportunity

3 the sooner the better

4 before it's too late

1 to seize an opportunity

2 to take advantage of situation

1 to take advantage of sb's difficulties (idiom)

1 to take advantage of a favorable situation

2 to seize an opportunity

1 to take advantage of sb's difficulties (idiom)

1 to loot a burning house

2 to profit from sb's misfortune (idiom)