Preferably collect the samples immediately after compost has been mixed or turned.

The number of points to be sampled will depend on the size of the pile, the state of maturity and  of the humidity % in which the material is found, the larger and more uneven it is, the greater the number of points that must be sampled and at different depths.

It is recommended to subsample from at least five locations and at each location collect 3 samples at different depths (near the surface, near the center, and in the center) and place them in a bucket.  Repeat this process at each sampling point.

When you have collected all the subsamples, mix the material thoroughly in the bucket. From this mixture, approximately 1 kg is collected, which constitutes the sample to be shipped to the laboratory.  

Avoid exposing the sample to the sun and high temperatures.