The word procedure just means everything you are going to do to carry out your investigation. Depending on the investigation this could be a series of experiments, detailed observations, or gathering data during fieldwork.
Make sure your plan is safe. Equipment must be set up and used in a safe manner. Usual laboratory safety precautions must be followed. Any possible hazards with chemical substances or biological samples must be checked before starting any experimental work. If you fail to carry out the experiment safely you will gain low marks for Obtaining evidence.