The proximity of Arica to the border with Peru makes it easy to reach in a short amount of time. You will want to go to the International Bus Station in the center of Arica, which is the open compound directly across the street from the Domestic Bus Station (Terminal Rodivario Arica)
It is less equipped than the domestic terminal, and does not look like much, but this is where you will arrive, and depart when travelling internationally. From here, for the easiest journey to most major destinations in Peru, you will be looking for a collectivo bus to Tacna in Peru. A collectivo is a smaller shuttle type bus that is a collective way for groups to travel, getting on and getting off at impromptu stops. It will take less than an hour to reach the border with Peru, and leaving Chile is much easier than entering, so usually moves through the border quite quickly. Once everyone is back on board, you will continue on to Tacna.
Depending on where the collectivo stops, you may have to walk a couple blocks to the National or Domestic Bus Terminal. This is where you will find a constant supply of buses to all main tourist hubs. If you are making an especially long journey, or a more obscure connection journey to somewhere more remote, check in advance, or call the bus station to ensure that when you arrive, you are not waiting hours for the next bus. If you are leaving to Arequipa, there are consistent buses and bus lines to choose from with a duration of roughly 6 hours and also departures to Cusco, Lima, Nazca and more.
Departing Arica in the direction of Bolivia, you will be presented with a few options, most of which, go through the biggest city, and bus terminal in the country, La Paz. Again, you will be departing from the International Bus Station in the center of Arica, but this time, instead of a collectivo bus, you will be boarding a proper, comfortable, tour bus that will be your steed for the whole journey.
The most visited destinations in Bolivia are Uyuni, to view the Salt Flats, Sucre, the countries beautiful capital, Cochabamba, Santa Cruz, and Copacabana, on Lake Titicaca, and as previously stated, the easiest and most cost effective way, is to make the transfer in La Paz, whether you spend time in the city or not. La Paz sits only four hours by bus from the border with Chile, and the border crossing of Tambo Quemado is very remote, usually making for short border lines and a relatively smooth crossing.
Once you arrive in La Paz, your final destination before your connection, will be the main Bus Terminal in the center of the city. From here, you will have options to go almost anywhere, even including three day buses to Buenos Aires! One thing you will also notice after doing the calculations in your head, the cost for buses here are roughly a third of what you pay in Chile, so jump for the full cama option of the big, comfy reclining seat if you are going on a long distance, and your bus has two levels.
From La Paz to Uyuni, takes roughly eight hours, Sucre roughly eleven hours, Cochabama approximately seven and a half, and Cocabana, a cool three and a half to four hours. If you’re making one of the longer journeys, it is recommended to get a morning bus leaving Arica, which will put you in La Paz in the early evening, giving you time to stretch your legs, grab some snacks or a meal in the bus station, charge your phone, use some wifi and take a couple hours before hopping on your overnight bus to your next destination.
Preparation is key during long distance travel and small steps in planning, knowing the hours, routes and locations of the terminals makes a long journey seem much shorter.