Normally extra safeguarding of the runway to ensure the ILS sensitive areas and obstacle free zone is not penetrated, eg using Cat II/III runway holding points and using specific runway entry/exit points. Also certain access points to the runway can be physically closed with barriers to reduce risk of runway incursion. It can also mean restricting the number of aircraft movements so as to keep a safe operation during the low visibility.
ATC and Airfield Operations would have specific checklists to complete before LVPs can be introduced.