One Way to Learn EsperantoNeedless to say, there are many approaches, each with its own merits. However, most depend on a shared common language between the instructor and the student. What if we don't have a common language? Couldn't we just mimic the method used for very young children? "What is that mummy?" The child points at or touches an object. The mother responds, "That is a glass." "What do you use it for?" The mother shows and tells the child that it is for drinking.
But do we have to go that far back? No. Being no longer children we know how to represent things and actions in writing. We have experience in using a language. As an example of a method that starts from basics, see the video "Benson - Universala Esperanto Metodo" and "A learn by showing - Benson Method", the source of its pictures.
It is important to note, that regardless of the method you use, very little real progress will be made by just watching and listening. The additional element needed is a lot of acting out of the meaning and using what you learn by speaking in Esperanto.
Both lernu and Duolingo Esperanto are good general starting points.