  We study the construction of the classical Becchi-Rouet-Stora-Tyutin (BRST)
charge and observables for arbitrary reducible gauge theory. Using a special
coordinate system in the extended phase space, we obtain an explicit expression
for the Koszul-Tate differential operator and show that the BRST charge can be
found by a simple iterative method. We also give a formula for the classical
BRST observables.
