Indeed, in addition to the above I would also avoid using things like PHPMyAdmin and Webmin if possible as they seem to have lots of security holes (especially the former). If you are just learning and this isn't a mission critical site with sensitive data don't worry too much about it but the more you can do without them the better IMO. Reducing your attack surface is paramount. Also, setup a normal user account with su privileges and use that rather than root when connecting to your server. Use SSH with public/private key pair encryption and disable password based login (only do this after making sure your keys work and /back them up/ haha). Keep up with security updates as well (esp. if you are running wordpress/other CMS or a forum with plugins). In any case stay safe out there and be vigilant!

EDIT: as @bleepbloop pointed out, DigitalOcean does have a lot of solid tutorials that are easy to follow along with.