Adding descriptive tags to each asset upon creation is the best way to improve searching and filtering in Content Builder. Tags are keywords that help you identify and categorize your assets based on different criteria, such as type, purpose, theme, etc. You can use tags to search for specific assets or filter them by one or more tags. Adding assets to folders upon creation is also helpful, but it does not allow you to assign multiple categories to an asset. Adding a description to each asset upon creation is useful for providing more information about the asset, but it does not help with searching and filtering.