Known ecoterrorism tactics include:
Sabotaging lab equipment.
Burning or bombing laboratories, production facilities, and construction sites.
Driving spikes into trees to prevent them from being logged safely.
Releasing caged animals. This is generally considered highly counterproductive for many reasons — for example, some become invasive species.
As a general rule, ecoterrorism is not widely supported by rationalists, who view it as a dangerous, overly-emotional response enacted with no consideration of the consequences. Regardless of whether the activity or business being targeted is operating ethically, it is highly disruptive to scientific research and a potentially serious danger to the environment in and of itself.