Phishing

Senders Address:

From a domain name that spoofs a significant brand, a known contact, or a coworker.

Subject:

Something quite urgent, worrying, or piques the victim's curiosity, so they do not ignore it and act on it quickly.
Eg: Your account has been compromised, Your package has been dispatched/shipped, Staff payroll information (do not forward!), Your photos have been published.

The Content:

Impersonating a brand or supplier: research their standard email templates and branding (style, logo's images, signoffs etc.) and make your content look the same as theirs.
Impersonating a contact or coworker, it could be beneficial to contact them; first, they may have some branding in their template, have a particular email signature or even something small such as how they refer to themselves
For example, someone might have the name Dorothy and their email is [email protected]. Still, in their signature, it might say "Best Regards, Dot".
Learning these somewhat small things can sometimes have quite dramatic psychological effects on the victim and convince them more to open and act on the email.