Indirect speech: 

With the exception of the existence of subjunctive mood, and the two forms of past tense, the following rules for reporting speech are essentially the same as those in English. 

Typically, we will introduce reported or indirect speech with a verbs like: said, explained, remarked, declared, etc. 

The tense of the original statement, represented in quotation marks, is a key to deciding the tense of the reported version of that statement.   

For example: 

Mary said:  "I want to go to the party."

Mary said (says) that she wants to go.   OR  Mary said that she wanted to go. 

Quiero ir a la fiesta.  --  Mary dice que quiere ir a la fiesta.  OR Mary dijo que quería ir a la fiesta.  (preferred) 

Mary said: " I´m going to read it."   

Mary dijo: “Voy a leerlo.”   --  Mary dijo que iba a leerlo. 

Mary said: I will read it. 

Mary dijo que lo leería. 

Mary said:  I went to the party with Marcos. 

Mary dijo: Fui a la fiesta con Marcos.   --  Mary dijo que había ido a la fiesta con Marcos. 

Mary said: I have gone to Colombia. 

Mary dijo: He ido a Colombia.   --   Mary dijo que había ido a Colombia. 

Future tense is also used to speculate about things in the present. 

I wonder who that is?   ¿Quién sera? 

That must be Jorge.   Será Jorge. 

Conditional tense is used to speculate about things in the past. 

I wonder who that was?  ¿Quién sería? 

Me must have been about thirty.   Tendría más o menos treinta años. 

I thought that there might be someone there who could help me.

Pensaba que habría alguien allí que  me pudiera ayudar.