1. **State the problem:** Evaluate the expression $3^{-2}$. 2. **Recall the rule for negative exponents:** For any nonzero number $a$ and integer $n$, $a^{-n} = \frac{1}{a^n}$. 3. **Apply the rule:** $$3^{-2} = \frac{1}{3^2}$$ 4. **Calculate the denominator:** $$3^2 = 3 \times 3 = 9$$ 5. **Write the final answer:** $$3^{-2} = \frac{1}{9}$$ So, $3^{-2} = \frac{1}{9}$.