Best way to learn linux.

Hello guys,

I just rented a server from digitalocean, the most basic one, and created a droplet with centos.

I'm a bit used to linux from the user level, but I've never been really an admin. I will start touching SLES 10 and 11 a lot in the next months, and so I would like to know which would be good tasks to train within the server. Everyday tasks you have to face and that can be used on a simple, almost empty, VM. I know there are some differences within the system, but I was used to fedora from a user prespective, so I thought about CentOS.

Thank you very much in advance!

PS: Thanks everyone so far! a lot of tips and I saved them all! :)