The local language in Tamanrasset area is Tamahak but most people speak Arabic and French. If you don't speak any French or Arabic you will need to have a guide as very few people speak English. Certainly people on the streets don't speak any at all so asking directions, ordering drinks and food and everything else has to be done in French or Arabic. Street signs also are never in English.
When visiting people's homes or going inside most buildings you will be expected to take off your shoes. This applies even to when you are camping in the desert and sitting on the mat in the sand around the camp fire, and when visiting nomads. Before you step onto, or sit on a carpet shoes must be removed.
The Tuaregs in the Tamanrasset area place great emphasis on greeting, shaking hands and asking how you are. There is a very formal set of greetings which starts with "as salaam halekum" then "hamdallah" and "labes" and only once you have gone through this procedure to a satisfactory level will they let you take photographs or talk.
English people with no French or Arabic will really have difficulties so it's much easier if you have a guide.
Gifts always help to break the ice. If you are a woman, take gifts to give to women as well as children.