Wavefront encoding is a crucial step in computer-generated holography, which converts the complex-amplitude wavefront on the hologram plane into a holographic modulating function. Since the digital element for complex-amplitude modulation is not yet available, current implementations of holographic wavefront modulation are carried out by phase-type or amplitude-type elements. The holograms are relatively converted to amplitude-only or phase-only forms. Herein, the phase optimization encoding and complex-amplitude converting methods of computer-generated holography based on liquid crystal spatial light modulators are introduced. The basic principle, range of applications, and algorithm flows are discussed, providing feasible strategies for various holographic implementations.