Designing RF PCBs requires careful attention to material selection, impedance control, and minimizing signal loss. Use low dielectric constant (Dk) and low loss tangent (Df) materials like Rogers RO4000 for high frequencies. Maintain consistent impedance with microstrip and stripline techniques. Keep signal paths short, avoid right-angle bends, and use finishes like immersion gold. Implement continuous ground planes and shielding to minimize EMI and crosstalk.