Keep a journal or a log of everything that happened leading up to, during, and after your accident.
Take detailed photos of the scene where the injury happened, as well as detailed photos of the surrounding area.
Inform the premises owner, employees, or security and make sure to ask for a copy of the incident log.
Take down the names, numbers, and emails of any witnesses who saw the incident occur.
Immediately seek medical attention and note where, when, and who treated you.