By default, WhatsApp will automatically set your privacy settings to allow any WhatsApp user to view your Read Receipts, last seen, profile photo and status. If you don't share your last seen, you won't be able to see other people's last seen. Please note there is no way to hide your online status.
To change these settings, simply go to Options > Settings > Account > Privacy.
You can individually set your last seen, profile photo and/or status to the following options.
Your last seen, profile photo and/or status will be available to all WhatsApp users.
Your last seen, profile photo and/or status will be available to your contacts from your address book only.
Your last seen, profile photo and/or status will not be available to anyone.
If you uncheck Read Receipts, you will not send Read Receipts. You will also not be able to see other users' Read Receipts.
Note: Read Receipts are always sent for group chats, even if you turn off the option in your privacy settings.