The SteamDeck is a fine piece of technology that is made by Valve for the primary purpose of playing video games or other entertainment activities. I have put together the resources, mostly for me, but hopefully it will be valuable for others too.
Steam Button Shortcuts
By holding the Steam key and pressing one of the many buttons or using the joysticks on the SteamDeck, you can invoke various actions. A menu of these actions can be viewed by pressing and holding the Steam button for 2 seconds.
Steam + B long press — force game shutdown
Steam + X Release Press — Show On-Screen Keyboard
Steam + L1 — Toggle Magnifier
Steam + R1 — Take Screenshot
Steam + L2 — Right Mouse Click
Steam + R2 — Left Mouse Click
Steam + Right Joystick — Acts as Mouse
Steam + Right Joystick (R3) Press — Left Mouse Click
Steam + Left Joystick Up — Increase Brightness
Steam + Left Joystick Down — Decrease Brightness
Steam + D-Pad Right — Enter Key
Steam + D-Pad Down — Tab Key
Steam + D-Pad Left — Escape Key
Desktop Mode
One of the great features of the SteamDeck is that Valve gave you access to a full fledged desktop computing interface with KDE Plasma. Here you can do all kinds of wonderful computery things and take advantage of the fact that this system is more than a console and can be used as a regular desktop or laptop kind of computer. Although not completely necessary, a Bluetooth keyboard and mouse is quite handy for this purpose.
To switch into desktop mode:
Steam Button > Power > Switch to Desktop

To Return to Game Mode. “Double-Click” on the Icon labeled: Return to Gaming Mode
Note: The video is accelerated and the time takes a bit longer than pictured.

Set up User Password
If you are going to use some of the really cool features of the SteamDeck, you will have to set up a user password. Technically, this is not strictly necessary but if you intend to access the device remotely, it would be a poor decision to not do this step.
Within Desktop Mode, open a terminal, specifically Konsole, and run this.
passwd
Enter your desired password twice to confirm it. Do note, you will not see the cursor move when keying in the password.
Enable Secure Shell (SSH)
To be able to manage files remotely using SFTP to add or remove game files. This is one of my favorite features. Sure, you can move things around using the SD Card but you can also manage the system remotely while you are playing games.
sudo systemctl start sshd
Determine the IP address of the SteamDeck in terminal
ip -c address
If you are connected through wireless look for the entry under wlan0 or sometimes wlp*** (where *** represents some sequence of characters. If the machine is connected through Ethernet on a docking station the IP address will be under the emp***. In this case, my IP address is 192.168.10.23.

You can, of course, get the IP address from the SteamOS interface or network manager when in Desktop Mode.
Immutable Root Filesystem
The SteamDeck has an arguably fantastic feature of locking its root filesystem making it immutable and essentially more resilient. What does it mean? You can’t make changes to it. Valve sends down updates to your SteamDeck in images that are specially tuned for the hardware. If you would like to make changes to it, you have to unlock it.
In the terminal run this:
sudo steamos-readonly disable
To restore the immutability of the root filesystem:
sudo steamos-readonly enable
Boot Menu
To boot from a different device, shut the SteamDeck down.
Insert a bootable Drive into the USB-C port or through a USB-C Hub or SD Card
Hold the volume down and power button. Release the power button when you hear the boot sound but continue to hold volume down for a moment longer. The boot menu will be displayed.

Performance Tweaks
Performance Boost and Space Savings by CryoByte33
Protective Cases and accessories
JSAUX Advanced Dock and Protective Shell for the SteamDeck | Review
JSAUX Screen Protector for the SteamDeck
Further Reading
SteamDeck | What Makes it Awesome for an openSUSE User
Fortnite on the SteamDeck | With Xbox Cloud Gaming
SteamDeck | RetroArch and mGBA for Trading Pokémon
Restoring SteamDeck Unresponsive Touchscreen