When sourcing small capacitors, you must prioritize Capacitance Value (measured in Farads) and Voltage Rating, ensuring the rated voltage is at least 20% higher than the circuit's peak operating voltage to prevent dielectric breakdown. Additionally, evaluate the Equivalent Series Resistance (ESR); low ESR is critical for high-frequency applications to minimize heat generation. For compact designs, specify the Case Size (e.g., 0402, 0603 for SMD or specific mm dimensions for radial types) and ensure the Tolerance level (typically ±5% or ±10%) aligns with your circuit's precision requirements.