When selecting antennas, you must prioritize Frequency Range (MHz/GHz) to ensure compatibility with your specific communication protocol (e.g., 5G, LoRa, GNSS). Key performance metrics include Gain (dBi), which determines signal strength and directionality, and VSWR (Voltage Standing Wave Ratio), which should ideally be less than 1.5 to minimize signal reflection and power loss. Additionally, verify the Impedance (typically 50 ohms) and Polarization (Linear or Circular) to match your system requirements.