>>1843570
It's more of a checklist than a guide, just start from the basic to the complicated, in an inside out manner.
Choose Hardware
Configure Firmware
Install and Configure OS
Install and Configure Server Software
Configure Network Interface
For hardware you want something stable. Redundancy is good but you can cheap out at the start, especially when you're learning. Some servers have redundant power supplies, hard drives, error correcting ram. You can buy a battery backup if you want but none of it is absolutely necessary for a game server because you won't need 100% uptime, but each helps. You can use any computer as long as it has powerful enough hardware to perform the function you need.
Firmware is important for rebooting the computer automatically from power-loss, or to automatically start/reboot the computer on a schedule in case of a crash or something. Decent firmware options make for fewer headaches.
OS is a case of selection for what you want. You can use anything that will just automatically start the server you want as a service/process, and then have a maintenance process that makes sure the server is running, hasn't crashed, and can restart the server process if necessary.
Software in terms of what services you want to be running, important for remote administration considerations too. Some server software runs better on windows, other is better on *nix. There are a lot of different factors for this. Either read up on others' experiences or try it all out yourself.
Network interface is about your choice, whether you want wireless or wired, what speeds, etc. A wired connection is preferable. You always want to over-provide for bandwidth. Go at least 20% over what you think would be comfortable. Double it if you can.
Once you have that sorted, then it's a matter of configuring the computer's firewall then your home gateway firewall/DHCP server for port forwarding.
The typical setup for a home server looks a bit like this: Home server (software firewall) <-> Gateway (firewall and port forwarding to home server) <-> Internet
You can configure your gateway firewall and port forwarding options for more security (like disabling all unnecessary ports for your home server), and then work on securing the server itself. If the ports are blocked in both places, the data won't go through, then you can focus on securing the ports that are open. Generally that works by recognizing hostile IPs and banning them. fail2ban is an example service/daemon for that function but there are lots of options.
Generally you want a game server to be completely independent from all your other hardware since there can be quite a few vulnerabilities within the server software. There were a lot of unpatched remote code execution exploits in source engine games, for example. Some people do this by packing the server into a virtual machine, but nothing beats true hardware isolation.
Managing the server itself then falls into either working on it in Remote Console within the server software, or you Secure Shell into the server OS to change server launch configurations and manually restart the server.
IT midwits try to make all of this seem way more complicated than it is so they can justify their salaries, and the super intelligent nerdy guys find it too simple to bother explaining. Combine that with search engines sucking jew dick and it's not easy to find a concise and simple guide.