I tried factoring by grouping and everything else I could think of but I can't seem to end up with a solution.

$\displaystyle r^3 - 6r^2 + 11r - 6 = 0$

Would there be a systematic way of factoring this or is it just guesswork?

The final factored form is:

$\displaystyle (r-1)(r-2)(r-3)$

Any help is appreciated!