This chapter introduces the core principles of fluid-particle coupling schemes essential for coupled CFD-DEM simulations. It systematically introduces the spectrum of coupling resolution including unresolved, semi-resolved, and resolved frameworks, which are defined by the ratio of CFDComputational Fluid Dynamics (CFD) cell size to the particle diameter. Then, the hierarchy of coupling directionalityCoupling directionality, from one-wayOne-way/two-way/three-way coupling to four-way coupling, which governs the degree of momentum and turbulence exchange between the fluid and particulate phases, are introduced. Furthermore, the chapter explains numerical implementation methodsNumerical implementation methods, including the averaged volume methodAveraged Volume Method (AVM) for unresolved coupling and the immersed boundary methodImmersed Boundary Method (IBM) for resolved approaches. Finally, the critical aspect of the computational sequenceComputational sequence and data exchange between the CFDComputational Fluid Dynamics (CFD) and DEM solvers is presented to provide a complete overview of the numerical workflow.