Random samples usually involve quadrats. A quadrat is simply a defined area so the organisms contained within it can be surveyed. The picture below shows a 50cm quadrat placed on a rocky shore
A good procedure for placing quadrats at random in the area we wish to investigate is to follow the steps below.
Place two axis at right angles along the edges of the area by using tape measures
Select coordinates on the grid created by the tape measures by using a random number table or the random number key on a calculator.
Place the quadrats at the coordinates generated.