Novice Question: Best way to log into root to do some admin things

I love FreeBSD so far; prepping to make it the host OS on my primary personal PC.

I installed KDE and see that I do have the ability to use su and sudo for various things. However, let's say I need to get a root command prompt before the desktop loads, what's the best way to do that? Single user mode? I so far have been using single user mode for some installs but I wonder if there's a more popular / useful way to log into root.

One thing I noticed when the system boots up into KDE is I get a login prompt but it pretty quickly disappears: i don't have time to enter root and the password. Can I / should I stop the desktop from quickly loading to log into root?
Another way is to simply don't run a (Xorg) display manager at boot. This way the machine always start in "console mode".
When you are ready to go graphical, simply login on a console as your user, and issue startx, startfce4 or whatever command that starts the desktop environment of your choice.
I like it this way, YMMV.