This review considers the many techniques that have been developed to enhance convective heat transfer. There is the desire to encourage or accommodate high heat fluxes. After introducing the techniques, the applications to the various modes of heat transfer (single-phase free convection, single-phase forced convection [including performance evaluation criteria, active techniques, and compound techniques], pool boiling, convective boiling/evaporation, vapor-space condensation, and convective condensation) are described. Comments are offered regarding the generations of heat transfer technology; advanced enhancement represents 3rd generation heat transfer technology.