Panama has three land routes from Costa Rica: the main border crossing along the Interamericana is at Paso Canoas, while a less-frequented border outpost is at Guabito, on the Caribbean coast, which allows for access to the Bocas archipelago. There’s a rarely used border post in the Chiriquí Highlands at Río Sereno (8am–5pm; reached by bus from Volcán).
Though you can take local transport and switch buses at the border, the slightly costlier fares on international services run by Tica Bus (wticabus.com) give you a better shot at an efficient and hassle-free passage (though border waits can be long). In addition to official documents, travellers at the border crossing will often be asked to show an onward or return ticket. If you’re travelling on a one-way ticket, migración is likely to require advance purchase of your bus fare back to San José.