How do I stop people from adding me to WhatsApp groups?

If you use WhatsApp frequently you should take a look at your privacy settings. By default, everyone can add you to WhatsApp groups, even strangers. Without changing this you can quickly find yourself in dozens of unwanted groups, including promotional ones, which can get annoying very quickly. Fortunately there is a simple fix - open the app and head to Settings -> Account -> Privacy -> Groups and select My Contacts. You can also exclude certain contacts by selecting My Contacts Except... and choosing which of your contacts can't add you to a group.