Turbulence modeling is at the core of modern Computational Fluid Dynamics (CFD), bridging the gap between theoretical fluid mechanics and practical engineering applications. This guide explores the fundamentals of turbulence, from the Reynolds-Averaged Navier-Stokes (RANS) approach and the Boussinesq hypothesis to improved RANS models like Realizable k-ε, RNG k-ε, and curvature-corrected models. With a focus on practical CFD applications, we delve into turbulence production limiters, near-wall treatments, and Fluent best practices. This structured study consolidates critical turbulence modeling concepts, equipping CFD engineers with the knowledge to select and implement the most suitable models for their simulations.