Best way to visit Algerian Desert (Djanet or Tamanrasset)

Hi,

I am planning to visit our desert, departure from Oran or Algiers (I have never been there). But I am not sure how to do so.

Shall I just book air ticket and hotel ? Shall I register with Travel Agency (If yes, I will be happy if you have recommendation) ?

I will appreciate if you can share your experience and the best way to spend few days in our beloved desert.