It is used as the preparatory subject in a number of structures.

It + be + adjective + of + noun/pronoun + to-infinitive

It was clever of him to find his way out.
It was unwise of me to lend her money.
It was foolish of him to reject the offer.
It is wicked of him to say such things.

The adjectives that are usually used in this pattern include the following: kind, good, generous, considerate, foolish, stupid, wise, unwise, clever, nice, wrong,  polite, brave, silly, wicked, cruel, careless etc.

It + be + adjective + to-infinitive

This structure is usually used to make general statements.

It is easy to learn English.
It is wise to give up smoking.
It is bad to tell lies.
It is impossible to lift the box.

It + be + no good etc. + gerund phrase

It is no good asking him for help.
It is no use arguing with her.
It was worth seeing the film.
It is worth visiting Egypt.

It + be + adjective / noun + noun clause

It is doubtful whether they will be able to help us.
It is strange that she should forget me so quickly.
It is a pity that she didn’t make another attempt.

It + take + personal pronoun + time expression + to-infinitive

It took me ten minutes to get dressed.
It took him two months to recover from his illness.
It will take you only five minutes to walk to the station.
It took me one year to learn English.