Normally, the tense in reported speech is one tense back in time from the tense in direct speech:
She said, "I am tired." = She said that she was tired.
Present Simple > Past Simple
"I always drink coffee", she said. > She said that she always drank coffee.
Past Simple > Past Perfect Simple
"Bill arrived on Saturday", he said. > He said that Bill had arrived on Saturday.
Present Progressive > Past Progressive
"I am reading a book", he explained. > He explained that he was reading a book.
Present Perfect Simple > Past Perfect Simple
"I have been to Spain", he told me. > He told me that he had been to Spain.
Past Perfect Simple - Past Perfect Simple
"I had just turned out the light," he explained. > He explained that he had just turned out the light.
Present Perfect Progressive > Past Perfect Progressive
They complained, "We have been waiting for hours". > They complained that they had been waiting for hours.
Past Progressive > Past Perfect Progressive
"We were living in Paris", they told me. > They told me that they had been living in Paris.
Future Simple > Present Conditional (Conditional Type I)
"I will be in Geneva on Monday", he said. > He said that he would be in Geneva on Monday.
Future Progressive > Conditional Progressive
She said, "I'll be using the car next Friday". > She said that she would be using the car next Friday.
You do not need to change the tense if the reporting verb is in the present, or if the original statement was about something that is still true, e.g.
He says he has missed the train but he'll catch the next one.
We explained that it is very difficult to find our house.
These modal verbs do not change in reported speech: might, could, would, should, ought to:
We explained, "It could be difficult to find our house." = We explained that it could be difficult to find our house.
She said, "I might bring a friend to the party." = She said that she might bring a friend to the party.
now > then / at that time
today > yesterday / that day
yesterday > the day before yesterday / the day before
last night > the night before
last week > the week before / the previous week
tomorrow > the next day / the following day
Reported Statements:
Present Simple Reported Statement Exercise (quite easy)
Present Continuous Reported Statement Exercise (quite easy)
Past Simple Reported Statement Exercise (quite easy)
Present Perfect Reported Statement Exercise (quite easy)
Future Simple Reported Statement Exercise (quite easy)
Mixed Tense Reported Statement Exercise (intermediate)
'Say' and 'Tell' (quite easy)
Reported Questions:
Present Simple Reported Yes/No Question Exercise (intermediate)
Present Simple Reported Wh Question Exercise (intermediate)
Mixed Tense Reported Question Exercise (intermediate)
Reported Orders and Requests:
Reported Requests and Orders Exercise (intermediate)
Mixed Exercises:
Reported Speech Mixed Exercise 1 (difficult)
Reported Speech Mixed Exercise 2 (difficult)