PARIS, March 27 — When getting rid of your smartphone, tablet or computer — whether you’re giving it to a friend, reconditioning it or selling it online — you should first make sure you’ve properly removed all traces of your personal data.

When it comes to your smartphone — a device that now holds your entire life (or almost), from vacation photos to administrative documents, emails and all your internet passwords — a few simple steps are all it takes to ensure that you don’t risk inadvertently sharing precious personal data.