Small. Even the biggest living things aren’t all that much bigger than we are, but there are lots of living things much, much smaller.
Active. Life doesn’t hold still, ever. It’s always trying something new, changing its environs or changing itself to adapt.
Wet. Squishy. Fluid. Water is life’s magic elixir. It doesn’t take much.
Patient. I was going to say "slow," but it’s a lot faster than your average geologic processes, even though it’s slower than most mechanisms we devise. We’re not quite as patient as life.