To use any available means or methods.
low-hanging fruit
Easily obtained gains; what can be obtained by readily available means …
catch some z's
To sleep.
catch on
To understand; to begin to understand; to realize.
catch a falling knife
To buy a financial instrument whose price is falling rapidly.
catch air
To make a jump.
catch big air
(Extreme sports) Superlative of catch air; make a big jump high off th …