How do you find the end behavior of  f(x)=3/x^2?

As $x \to 0 , f \left(x\right) \to \infty$.
Also, as $x \to + \infty \mathmr{and} - \infty , f \left(x\right) \to 0$. f(x) has thus a vertical asymptote x=0 and an horizontal asymptote y=0.