This work presents approximation methods that are used to identify Bit Error Rate (BER) expressions which are frequently utilized in investigation and comparison of performance for wireless communication systems in the literature. In this group of approximation methods, some expectation integrals, which are complicated to analyze and time-consuming to evaluate through Monte Carlo simulations, are handled. For this group of integrals, by using the sampling property of the Q-function under mid- and high- Signal-to-Noise Power Ratio (SNR) assumptions, reliable BER functions revealing the diversity and coding gains are derived. Although the methods we proposed cover a larger class of integration problems, the results presented in this work show the step by step derivation of the BER expression for a canonical cooperative communication scenario starting from basic building blocks. The derived expression agrees with the simulation results even under relatively low SNR values.