Whenever you simplify a square root or a cube root you are writing them in the simplest form.
This video teaches a factoring method.
The factoring method Involves factoring the numbers under the radical. If the problem is a square root look for pairs, and for cube roots look for triples of the same number.
0:09 Simply 3 x the cube root of 32
1:20 Simplify 4 x the cube root of 27
1:59 Simplify the square root of 18x over a^6