Chad Perrin explains step-by-step on TechRepublic how to keep a FreeBSD system up-to-date:

Certain operating systems make this easier than others, as do certain applications. FreeBSD in particular offers specific explanations of gotchas and difficulties that might affect users when software is updated, and also makes it easy to audit installed software for vulnerabilities. In cases where a test network and the resources of research in depth are unreasonable expectations, the key to ensuring upgrades go smoothly without breaking things is to have a step by step process for updating that makes minimal research easy to perform and directions for solving updating problems before they affect your system easy to find and follow. Thanks to the UPDATING notes provided by the FreeBSD Ports system, such a process is easy to develop.

The way I handle software updates on FreeBSD starts when I install FreeBSD. Once the OS is installed, I also install the /usr/ports/ports-mgmt/portupgrade port. This is a set of scripts that automate and simplify the user interface to the Ports system. You can read more about it and how to get it set up in the FreeBSD Handbook. Next, I use the portinstall command provided with portupgrade to install the portaudit tool. You can find information about it, too, in the FreeBSD Handbook.

Then, every time I need to update software, I follow a procedure that looks something like this: