The main source for learning new vocabulary are the different dictionaries. By working out the meaning of words dictionaries include important words used in every day speech.There are enough examples to show the vocabulary in a different context to extend the knowledge and draw attention to typical collocation.
The dictionaries are monolingual,bilingual or multilingual. The monolingual are very important because they give people much greater confidence when approaching new texts and increases their independence when reading,listening or talking.
So,the most common used way of learning vocabulary is to look at any dictionary and find the meaning of the word either in your mother tongue or to guess its meaning. But you cannot look up every word in the dictionary.
There are other ways to learn new vocabulary. One of them is to work out the emaning of words from the context or to look at the part of speech.It is easy,does not waste time as to look at the dictionary and search for the word and its meaning.
Another way is to listen to persons who speak the language well. Do not be afraid to ask them the meaning of a word they use that is not familiar to you.
Make your vocabulary notebook or index cards you can use for playing game with yourself. Use the new words by talking or writing every day. When you use the word in different situations this means that you remember it.
You can stick labels onto the walls or on important places at home or at your office and every time you are around them,look at them and repeat their meaning by using them.
Put in your pockets some sheets of paper where your new vocabulary is written by you. While you are traveling to your school,college or work have a look at the words. At any time of the day you can look at sheets and repeat the vocabulary.
You can find your own ways to learn new vocabulary my task was only to show you some of these that I have used.