Lock WhatsApp: Apart from your phone, keep your WhatsApp also password protected so no one accesses your chats
Block WhatsApp photos from appearing in photo roll: Exclude WhatsApp from photo roll so if it gets hacked at least your personal pics are safe
Hide 'last seen' timestamp: Although, it may not be a vital information, but for some scammers it can be
Restrict access to profile picture: Allow only those to see your profile pictures whose numbers you have saved
Watch out for scams: WhatsApp never sends you messages or email, if you receive one then be careful of it
Deactivate WhatsApp if you lose your phone: Try logging in to your WhatsApp from another sim, it will block your app if stolen
Be careful what you talk about: Try not to send your personal information like address, pictures, etc to anyone on WhatsApp