As with any OS, keep it up to date is very important. It helps avoid problems due to bugs and security vulnerabilities. In some cases it also helps add new functionality in some cases. The command to do the updates is sudo apt-get upgrade. This will start the process of checking which installed items have upgrades available.
If you want to do a trial run before committing to an upgrade, you can do sudo apt-get update which should download the latest list of available updates. Another option is to do sudo apt-get s upgrade which will run a test of the upgrade process without installing any of the packages. This can give you an idea of how many updates you may need and the approximate time it will take to download and install them. The s you see after apt-get is the flag that tells upgrade to not download or install anything.
Depending on how you plan on working with iptables or some of the other advanced features, you probably should get the latest ca or certificate authority certs install on your Raspberry Pi. You can do this by using the sudo apt-get install ca-certificates command to install latest certificates.
As I learn more about Debian/Raspian, I will post additional entries to share what I am learning.
To see more of my posts about the Raspberry Pi, please go to http://www.ronnutter.com/category/raspberry-pi/