Make sure your operating systems and applications are always updated. Use Two Factor Authentication (2FA) when available. Don’t click on suspicious links, even if the sender is in your senders list. Disable default user name and password on all devices. Do not leave your Wi-Fi, Bluetooth or others connection protocols active if you don’t need them.
Make your passwords complex; you can always use a good password manager so you only have to remember one password. Don’t use the same password for all accounts, especially for important banking or financial applications or connections.
Always check the permissions an application requires from your device before installing it. Also always make sure you are downloading or installing from a trusted source. Do not jailbreak your iPhone.
WhatsApp is good, Signal is better. Make sure to set messages to auto-delete if you do not want to keep a record of a conversation. Also never back up your chats on the cloud or any external service that you do not control. The cloud is just your data in someone else's computer. Use GPG for email encryption, or Hushmail.
Use Tor Browser for perfect anonymity and no tracking. Don’t enter personal information on websites or pop-ups without verifying that it is legit. Always check for HTTPS. Don’t use the same email address for everything. It’s easy to create new addresses that you use just for certain important accounts. That will limit your exposure to spam, phishing and scam emails.
A VPN is a great way to browse the internet anonymously without having your ISP, or anyone else, snoop on what you are doing. It is also a good way to circumvent internet restrictions that you sometimes ome across geographically.