When evaluating mountain bikes, prioritize the frame material, typically 6061 Aluminum Alloy for a balance of weight and durability, or Carbon Fiber for high-end performance. Ensure the drivetrain components (derailleurs and shifters) are from reputable brands like Shimano or SRAM to guarantee shifting reliability. For suspension, verify the travel distance (typically 100mm-120mm for XC or 140mm+ for Enduro) and check if the hydraulic disc brakes meet international safety standards for stopping power.