Guided waves, particularly Lamb waves, are fundamental tools in Non-Destructive Testing (NDT) and Structural Health Monitoring (SHM) for the inspection of plate-like structures prevalent in aerospace, energy, and civil engineering. The effectiveness of Lamb wave-based inspection hinges critically on the ability to selectively excite and interpret specific wave modes, a task complicated by their dispersive and multi-modal nature, especially at higher frequencies. This chapter presents a detailed numerical investigation using the Finite Element Method (FEM) to explore Lamb wave propagation in a representative thin stainless steel plate. We systematically compare the efficacy of two common excitation techniques – concentrated normal force and prescribed boundary displacement – at both low (0.6 MHz mm) and high (6 MHz mm) frequency-thickness product regimes. A two-dimensional Fast Fourier Transform (2D-FFT) analysis is employed to decompose the resulting wavefield in the frequency-wavenumber domain, allowing for clear identification of the excited modes against analytical dispersion curves. Our findings indicate that while both excitation methods effectively generate the fundamental anti-symmetric (A0) mode at low frequencies, with force excitation offering simplicity, displacement-based excitation demonstrates significantly superior mode selectivity at high frequencies, preferentially targeting the A0 mode amidst other potentially interfering modes (S0, A1). The inherent challenge of multi-mode coexistence, especially at higher frequencies, is highlighted, underscoring the need for careful consideration of excitation strategy based on the specific inspection requirements. This study provides foundational insights into Lamb wave excitation physics and offers practical guidance for optimizing NDT/SHM procedures involving guided waves in thin plates.