Stores give out Promo Packs at their discretion.
Stores will be responsible for managing their promo pack quantities throughout each season.
All-foil promo packs are suggested for 1st place prizes in tournaments as well as for events that cater to players that want to show off their decks (Commander events, for example). Premium Promo Packs say Premium on the outside of the pack.
Wizards recommends against issuing Promo Packs at Prerelease, since WPN members receive booster packs to use as prizes.