Light beams can carry spin as well as orbital angular momentum. Most lasers, however, emit light beams of zero orbital angular momentum, which have planar or spherical phase fronts. We discuss how these beams can be transformed into laser beams of nonzero orbital angular momentum, which have twisted phase fronts. Experiments for realizing such beams will be described and their phase an polarization profiles will be discussed. Observations of many unexpected features, when these beams are used in interference, diffraction and polarization experiments, will be presented.