Quality over quantity
20 accurate citations on authoritative directories beat 100 on random low-quality ones. Google's algorithm now weights citation authority heavily.
The priority list
Google Business Profile, Facebook, Yelp, Bing Places, Apple Maps, industry-specific (Houzz for home services, Tripadvisor for hospitality). That's 80% of citation value.
Consistency is non-negotiable
Name, address, phone must match exactly across all citations. One typo and the citation either gets discounted or actively hurts.