  In these lectures, I describe the techniques used within the QCD sum rule
approach. The basic concepts of the approach are introduced using a simple
model of quantum-mechanical oscillator in 2+1 dimensions. Then I discuss their
field-theoretical extension and the construction of the operator product
expansion for current correlators in QCD. The calculation of static parameters
is illustrated on the example of sum rules in the vector and axial meson
channels. Finally, the QCD sum rule calculation of the pion electromagnetic
form factor is presented as an example of application of the method to dynamic
characteristics of the hadrons.
