When this happens, he figures out how long it all takes. Light experiments with a number of unique, interesting deaths when he first starts out as “Kira” in order to test out the Death Note’s limits. 3) “After writing the cause of death, details of the death should be written in the next 6 minutes and 40 seconds.” So, you have to think really hard about someone’s face and write their name at the same time. Without a specific face to attach to a name, the Death Note’s effects don’t take hold. If you’re wondering why writing a name like “John Smith” won’t kill all John Smiths, it’s because of this rule, which becomes a major plot point in the original Death Note. Therefore, people sharing the same name will not be affected.”
2) “This note will not take effect unless the writer has the person’s face in their mind when writing his/her name. When they died of a mysterious heart attack, Light’s world changed forever. In the anime and manga, Light - who initially thought the Death Note was a bad prank - wrote in the name of a criminal who was holding people hostage.
The default cause of death is usually a heart attack, unless the owner of the death note specifies a different cause. The most basic rule in Death Note is this: Whoever’s name is written in the book will die.