Allow multiple selection
When searching for specific criteria, like vacation lodging for a large group, there's often a need for multiple selections within a single filter category. For instance, you might require multiple beds, pet-friendly, smoking allowed, wifi, air conditioning, breakfast, and nearby dining options.
Functionally, radio buttons allow only one selection. Unless the options eliminate each other, checkboxes provide a more flexible search. So make sure your filters incorporate checkboxes for categories where multiple options can be selected.
Pro Tip: Use visually standard checkboxes — a small square with a checkmark or an (X) when selected.