The obvious evidence you need to preserve for a successful premises liability lawsuit is the condition that caused you to be harmed. Whether it is a wet spot on the floor or an uneven step, it is imperative that you take pictures as soon as possible because, oftentimes, the property owner will come in and fix the hazardous condition in response to the accident.
Other evidence you might want to preserve is the footwear or clothing you were wearing at the time of the incident. In the case of a slip and fall accident, for example, these items will often identify the substance that caused the fall. Think of a smudge or wet spot on your clothing after you landed on the floor, or a scuff mark on your shoe that caught the edge of the elevated sidewalk.
Lastly, you need to collect and save the names and contact information of any witnesses. Unless there was a crime committed, the police may not come to the scene of a premises liability incident. Therefore, you must gather that information yourself. Otherwise, those witnesses may be lost forever.