How to format and re-install when reselling?

[mbpmpb17]

I want to prepare my laptop for selling.

How can I reformat the drive in a secure way, and also re-install Sierra on my laptop? (I don't have the install CD).

My computer does have a CD drive (2010 MBP).

 

[medulla]

I want to prepare my laptop for selling.

How can I reformat the drive in a secure way, and also re-install Sierra on my laptop? (I don't have the install CD).

My computer does have a CD drive (2010 MBP).

https://support.apple.com/en-us/HT201065

 

[ZapNZs]

What I've settled on is (after deauthorizing any respective accounts):

• Enable FileVault if not already enabled, and allow it to encrypt all contents on the computer's drive(s) (I believe this step is more important than ever before)
• Then, boot into the Recovery HD (or, create an install/recovery USB flash drive, boot into USB Recovery drive), open Disk Utility, (unlock the drive(s) if necessary), erase the partition(s) with any OS(s)/User Files
• Then, close the Disk Utility, and select the option to reinstall OS X