When charging at a public station, you'll likely use a charger that's serviced by a network. Many have membership programs or subscriptions (you can download the app on your phone) and you can also pay as you go. Rates vary by network - some charge by session, per kWh, by the hour and some are free.
Membership with these networks usually includes a member discount or if you're not a member you can call the 24-hour customer service line to pay on the spot.
Blink Charging, ChargePoint, Electrify America, EVgo, Greenlots, and SemaConnect are the most common network providers in the U.S.
Finding Public Stations
Resources and apps like PlugShare, Chargeway, or the Alternative Fuels Data Center give real-time information on charging station locations, pricing, nearby amenities, and availability. Google Maps also now shows charging station locations.