What's a good way to get started in Space Station 13?
Solution 1:
Welcome to the station! Or as Magneto puts it, welcome to DIE!
You're going to die a lot on Space Station 13. Even on a good round, when you do everything right and know all the rules, there's a very good chance you will die in some unexpected way. It's a lot like Nethack or Dwarf Fortress in that way.
The good news is that when you DO die, there are ways you can keep participating despite your death! For one, in the OOC tab, you have the option to become a Ghost and observe the action taking place around the station. This is a good way to get acquainted with the layout of said station, and to see what some of the things going on might be.
Certain servers have a wikipedia page that offer their own "beginner's guide", which you can usually access with the Wiki tab. These guides will get you started with some basic knowledge on how things work.
Basically, you interact with the world by clicking on things. You click on things to pick them up, you click on things to use them on other things, and you click on a thing in one hand on a thing in another hand (Switch hands by clicking the hand you want to use) to use the thing on the other thing. And there are a LOT of ways to interact with things! It can be pretty daunting, especially on your first time, so I do recommend finding at least one guide that can explain basic controls. There are a few out there, such as the Baystation 12 one or the /tg/ station one. But find one that works for you.
A good way to get acquainted with the station and to get around it (You walk into a door with the arrow keys to go through it, by the way) is to be an assistant. They have basically no responsibilities, and access to various maintenance shafts with interesting things to pick up and put on (to the left of your screen is an icon that opens up your character doll, and allows you to put on various things). You will still probably be a target of someone, but with each death you'll learn a little more about how the station functions.
Once you get your legs for the stations, start picking a few civilian jobs to get your feet wet. Learn to mix drinks as a bartender to learn the basics of mixing liquids, or be a chef and learn the basics of adding items together to make other interesting items. Grow plants in Botany and learn how to harvest mad crops, be a librarian and have nothing really to do of importance. Be a Cargo Tech (Recommended!) and deliver important supplies around the station. Most importantly, don't get frustrated if you die a few times. Life is fast and loose and can even be returned to you in a few fun ways.
And by all means, ask people how to do things (In character! Or without referring to what you're doing if you're doing it in OOC, or click the admin tab and ask an admin for help). In fact, talking things out with people and acting as clueless as you really are not only helps you learn to do different jobs, but builds roleplaying ambiance that really is at the heart of enjoying Space Station 13.
Solution 2:
The first place to start is the relevant wiki. Each server is either derived from a goonstation or a /tg/ server branch, and so there is a different wiki for each.
Use the wiki to familiarize yourself with basic controls, and test them out in-game. It sounds like you have a grasp of them already.
Next, use the wiki and pick one of the lower level science jobs to try. I suggest something like botanist or roboticist. When you spawn, immediately go to your lab following the map on the wiki. While you may be able to figure out how to do the job just from the wiki, you hopefully can ask someone else in that role (there can be multiple people in the low level science roles). Start with the basics, making food for the cook or turning people into cyborgs. From there, you can try a different job or try the more advanced mechanics and concepts.
Many people advise that new players start as an assistant. This is terrible advice, because assistants can't do virtually anything without breaking space law, unless they get permission from someone else. Not only that, but they also spend their time wandering the halls, which is where the chaos starts. Its usually much safer in a science lab.
Solution 3:
Don't start as security, start as something like medical doctor, or shaft miner.
Throw yourself into it, don't be afraid to ask questions from the admins using the "adminhelp" command. Know where the wiki is, you're going to have it open. A lot. If you get killed, and an admin replies "valid" don't go screaming in OOC or in dead chat that you got griefed, randomly killed, etc. For the love of god, read the rules for the server you're on, many servers have different ways of running things and it can be frustrating when someone gets banned for one thing on one server, when they came from another server and it was okay to do that thing.
Thats the basics, pretty much.
Oh, I'd avoid using OOC to ask questions about in game events or how to use some items, that's best using the adminhelp command.