Algeria is a huge country and travelling between major cities can take a lot of time and nerves as well, while the distances in the more populated north are not so big and a trip from the east to the west can be done in a 12 hours on highway. Travelling to cities in the Sahara is more difficult since the south is barely connected with good roads, train and bus connections.
It's usual to take a taxi to travel between near cities or in cities, the prices are pretty moderate but when travelling between bigger cities with large distances taxis are the same or more expensive as flying. Try to avoid unoffical taxis since it's very likely the driver will rip you off. Most Taxis have no taxmeter so arrange a price in advance. Many drivers will try to take advantage of your lack of knowledge but never pay more than 30 DA per KM regardless of what you are told. Tipping is not nessecary but you can round up to the next 10 Dinars.
The Algerian Railways are operated by SNTF (http://www.sntf.dz), currently the trains and lines are being modernised. Ten comfortable highspeed trains named Autorail were bought, currently two of them are in operation. Tickets can not be bought online, only at the train stations, prices are quite moderate but more expensive than buses or taxis but in return you will have more comfort and enjoy wonderful landscapes.
Main Routes :
Algiersto Oran , the train takes 4 hours and departs each day at 15:00 from Algiers Central Station and arrives in Oran at 19:30, 2nd Class: 1.000 DA, 1st Class: 1.500 DA.
Algiersto Annaba, on this route there's a only a slow and less comfortable nighttrain, departing each day at 20:45 and taking all the night for the way to Annaba. As an alternative you can catch the daytrain to Constantine and take from there a cheap taxi to Annaba.
Algiersto Constantine departing each day at 06:45 and arriving in Constantine at 13:30, make sure that you get a window seat because the train will take you through the scenic kabilyan mountains and wonderful landscapes, 2nd Class: 1.200 DA, 1st Class : 1.800 DA.
From Algiers you can reach almost every major Algerian city by plane, and it is highly recommended to take a flight when travelling longer routes and to Saharan cities. Houari Boumediene, in Algiers, is the biggest airport in the country; there are other airports in major cities like Oran,Constantine & annaba.the other airports are basic .
Air Algérie (http://www.airalgerie.dz/) is the national carrier with many flights to almost all Algerian cities with an airport. The prices vary regarding of the length of the flown route; airfares to smaller and Sahara cities tend to be pricier than between bigger cities such as Oran to Algier. The airline uses Houari Boumediene Airport as its hub, and almost all flights start or land there. There are seven daily flights to Oran from Algiers and five daily flights to Annaba and Costantine. Other destinations served from Algiers daily or several days weekly are Adrar, El Oued, Tebessa, Batna, Biskra, Sétif, In Ames, Tindouf, Timmoun, Tlemcen, Tamanrasset, Tiaret, Tebessa, El Goela, Ouaragla, Hassi Mesaoud, Bejaia, Ghrardaia, Tlemcen, Illizi, Djanet, Touggourt, and Béchar.
The road network is well developed in the north, the Algeriean goverment has made much improvements in the last years regarding road building, new highways were built to replace the already marod roads. The most important highway is the 1200 km long N1 Route est-ouest from Annaba to Oran, almost all bigger cities in the north are connected to this highway including Algiers.
A car is not absolutely necessary because of the well running public transportation system, but could be sometimes useful to reach more remote areas. Keep in mind that driving habits are completly different compared to western norms and that rules and prohibitive signs are more seen as guidelines, even by the police! It would be a wise decision letting a local algerian do the driving for you in the first days to get an impression of the driving style, if this is not possible it's recommended to stay on the highways.
Do not try to reach saharan areas with another car than a 4x4, occasional dunes on the roads and extreme temperature changes will offer a challenge for the driver and the car.
Fuel is extremely cheap and will not cost more than 23 DA per liter.