It's true that you can learn new words when you read or listen，but you should also study new words seriously.Here are a few things I do.
    Make flashcards.I find this is really the best way to learn new words.Make some small cards and write the words on one side and either the words in your language or the meaning in easy English on the other side and test yourself.To make this work，you have to review as often as possible.
    Make sentences with the new words.This is great if you can ask someone to check them.It is also great to make up crazy sentences.In that way you won't forget them!I also collect example sentences of the words I'm trying to learn.If I see the word from a book，I write down the sentence.
    Make up a mnemonic （助記符號(hào)）.A mnemonic is a way to remember something，like a short story.For example，if I want to remember the Japanese word "yukkuri" （which means "slowly"），I could think about the English words "you" and "curry"，and maybe imagine someone eating a plate of curry very，very slowly!
    Put signs with English words on things in your house.For example，I put the word "kitchen" on the kitchen door.The problem is that it works for a while and then you get used to the words and forget to read them!

（1）Is it great to make up crazy sentences？

Yes，it is.

Yes，it is.

（2）What does the writer think is the best way to learn new words？

Making flashcards.

Making flashcards.

（3）How many ways of learning new words are mentioned？

Four.

Four.

（4）What is the problem for us with putting signs on things？

It works for a while and then you get used to the words and forget to read them.

It works for a while and then you get used to the words and forget to read them.

（5）What is the passage about？

A few things to learn new words.

A few things to learn new words.