Use the rational roots test. The possible roots are: plus/minus 6,3,2,1
Use synthetic division and you will see that 3 is a root:
3 | 1 -3 -3 11 -6
| 3 0 -9 6
____________
1 0 -3 2 0
Use rational root again, to see that possible roots are: plus/minus 2,1
Try 2:
2 | 1 0 -3 -2
| 2 4 2
_____________
1 2 1 0
The above is x^2+2x+1 which is a perfect square: (x+1)^2
So we have the final factorization: (x-3)(x-2)(x+1)^2
So the roots are: 3, 2, -1
Where -1 is a double zero.