What to do when one sees a bad dream.

It was narrated that Abu Qutaadah said: The Messenger of Allaah (peace and blessings of Allaah be upon him) said: 

“Good dreams come from Allaah and bad dreams come from the Shaytaan. If anyone sees a bad dream that scares him, let him spit drily to his left and seek refuge with Allaah from its evil, then it will not harm him.”

(Narrated by al-Bukhaari, 3292) 
It was narrated from Jaabir that the Messenger of Allaah (peace and blessings of Allaah be upon him) said: 

“If any one of you sees a dream that he dislikes, let him spit drily to his left three times and seek refuge with Allaah from the Shaytaan three times, and turn over onto his other side.”

(Narrated by Muslim, 2262). 
It was narrated that Abu Hurayrah said: the Prophet (peace and blessings of Allaah be upon him) said: 

“If any one of you sees something that he dislikes, let him get up and pray, and not tell people about it.”

(Narrated by Muslim, 2263). 

So we may sum up from these hadeeths that when a person sees a dream which he dislikes then he:

1. He should spit drily to his left three times, i.e., blowing with a little bit of saliva.
   
2. He should seek refuge with Allaah from the accursed Shaytaan.
   
3. He should seek refuge with Allaah from the evil of this dream.
   
4. He should turn over from the side on which he was sleeping, so if he was lying on his left side he should turn over to his right side, and vice versa.
   
5. He should get up and pray. 
   
6. He should not tell anyone about it.
   

And Allah knows best.