Costa Rica is an easy country for independent travel, with the most developed tourism infrastructure in Central America. These are the things worth knowing before booking.
Car hire: the insurance
This is the single biggest source of unpleasant surprises. Costa Rica has a compulsory third-party liability insurance that is not included in the very cheap rates shown on comparison sites, and that your credit card does not cover. It is charged at the counter regardless, and it can double the advertised price. Book with companies that show it itemised from the start.
A car gives real freedom, especially for Nicoya and the north. But do not drive at night outside the main highways: there are deep potholes, animals, unlit cyclists and single-lane bridges. Download offline maps.
Getting around without a car
Public buses connect essentially the whole country, are very cheap and reasonably comfortable, though slow and with timetables that are opaque if you do not speak Spanish. Shared tourist shuttles cover the main routes door to door at a middling price and are the sensible option for most visitors. There are also short domestic flights with Sansa between San José and the coastal destinations, which save entire days of driving to Osa.
Money
The currency is the colón, and US dollars are widely accepted, though at poorer rates in small businesses. Cards work almost everywhere; carry cash for sodas, buses and rural areas. Restaurant bills already include a ten per cent service charge plus tax, so an additional tip is not obligatory — though it is customary for guides and drivers.
Health
Tap water is drinkable across most of the country, including San José and the main tourist areas; in remote rural zones, use bottled. There is dengue risk in the lowlands: use repellent. There is no malaria in the usual tourist areas. Private healthcare is good, with hospitals in San José, Liberia and Nicoya.
Safety
The country is calm by regional standards, but opportunistic theft is common: never leave anything visible in a car, not even briefly, and least of all at beach or trailhead car parks. Use the accommodation safe. On beaches, beware of rip currents, which cause most drownings: if caught, swim parallel to the shore rather than against the current.