Do you want to learn new vocabulary in a very efficient way? Use flashcards

Do not worry too much if you forget a word; it happens to everyone. In such situation just act as natives do: use so-called “fillers” of the conversation, such as er, um and carry on as if nothing happened. Try also “beating around the bush”: if you can’t remember a given word, try to describe what you have on your mind using other words or definitions.