At bus terminals, you usually buy your bus ticket at a front desk. It is wise to be there some time in advance to assure you have a spot on the bus. When you enter the bus at a bus stop, you pay directly to the driver. Note that public buses are usually paid in cash and local currency. Bus drivers usually have little change, so it's best to have the exact amount ready or carry small bills and coins. It is also a good idea to bring snacks and water with you. Many bus routes in Costa Rica don't have food or drink options, while you might be driving for a couple of hours in some occasions. Note that theft can be an issue when travelling with public transport, so please be vigilant and keep your belongings with you at all times.

Besides theft of personal belongings during the ride where you should be vigilant for, there is also a well known bus scam used on tourist who walk in the direction of a bus terminal. The Terminal 7-10 in San José where the bus to La Fortuna leaves is a well known target location. What happens is that locals, mostly taxi drivers, start talking to tourists. They convince you that for whatever reason there are no buses leaving that day and that your best and only option is to take the taxi to your final destination or to a bus station, from which, they convince you, are buses leaving to your destination. Once they have convinced you, they most likely will bring you to said place, but obviously charge you greatly for their "kind" service. Note that these people might even be official taxi drivers with an official red taxi and appear very kind and helpful with a solid story why buses don't drive that day. When this happens to you, simply thank them for the information and continue walking to the terminal.  

While the bus network in Costa Rica is extensive, some destinations may require multiple transfers, which can be time-consuming and inconvenient, which increases the chance of missing a connection or getting stranded for a day. Figure out the bus schedules beforehand as much as possible, and be flexible in your itinerary. Sometimes a more expensive tourist shuttle might be your best option. There are also Facebook groups where people ask for, or offer to, ride-along with tourists who rented a car, or for sharing shuttles to share costs. Don't be afraid to ask for help to locals. Locals in Costa Rica are generally friendly and willing to help travelers, so don't hesitate to ask your questions. While English is often spoken by people working in the tourist sector, bus drivers and fellow passengers may not. Knowing some basic Spanish might help a lot.

Recommended websites for planning a bus trip and comparing different options with travel times and prices are the Rome2Rio website or the Moovit website (shown below). Moovit is also available as a mobile App. If you use the Moovit website prior to your visit to Costa Rica, make sure you set the country to Costa Rica, as it will by default select the country you are currently in. You can only choose starting and destination points from the selected country.  You can change the country settings in the upper left corner next to the Moovit logo.

On the Visit Costa Rica webpage, you can download a bus itinerary that contains a lot of valuable information when travelling with public transport. The download includes an extensive bus schedule with departure times and addresses of terminals and schedules of ferries and boat connections and international road transport to for example Nicaragua and Panama. When travelling to the Caribbean side of the country, note that the bus schedule contains two destinations that are called Puerto Viejo. Puerto Viejo de Talamanca is located in the Limón province at the South-Caribbean coast. Puerto Viejo de Sarapiqui is located in the Heredia province in the Northeastern part of the country. Both are very nice destinations, but when traveling to Puerto Viejo make sure you pick the one you intend to travel to.