1.You should avoid clicking on random links come across or downloading attachments from unknown or unexpected sources; it might be on your social media account or through emails.
You can be on your guard, and stay conscious about not clicking random links, but then make the mistake of giving your devices to a someone you consider trustworthy, and they are not as conscious as you are, they make the mistake of clicking random links, and even though they do not nurse the intention of evil towards you, they end up putting you in a difficult position that they do not even know off. If you must give someone you trust your personal device, be sure of their security consciousness.