The lepton plays an important role in the physics program at the Large Hadron Collider. Spin of the lepton represents an interesting phenomenological quantity which can be used for separation of signal from background in searches for New Physics processes or in measuring properties of New Particles decaying to leptons. A proper treatment of spin effects in the Monte Carlo simulations is important for understanding the detector acceptance and for measurements of polarization and \tau spin correlations. The TauSpinner package is a software tool allowing to modify spin effects in any event sample containing leptons. By calculating spin weights, attributed on the event-by-event basis, it enables numerical evaluation and/or modification of the spin effects on experimentally measured distributions. We review a selection of simple distributions which can be used to monitor longitudinal spin effects in decays. New methods, with respect to previous publications, for validation of spin content of the user-prepared event sample are provided.