Find the derivative (f'(x))
Solve (f'(x)=0) and note where (f'(x)) is undefined
Use those values to split the domain into intervals
Test the sign of (f'(x)) on each interval
If (f'(x)>0), the function is increasing on that interval
If (f'(x)<0), the function is decreasing on that interval
Write the intervals using interval notation