What is the best way to upgrade Debian Jessie?

[Linux for blind general discussion]

My installation was made in October 2016. It's showing some quirks and the last apt-get oonly upgraded one package.

Thanks,
John

-- 
John J. Boyer
Email: john.boyer at abilitiessoft.org
website: http://www.abilitiessoft.org
Status: Company dissolved but website and email addresses  live.
Location: Madison, Wisconsin, USA
Mission: developing assistive technology software and providing STEM services 
        that are available at no cost