It's fine taking from demos, but don't expect them to be plug-and-play, you're going to have to do a lot of tweaking to existing systems in order for them to fit into your game.
People will be glad to help you as long as you spell things properly and explain your problem.
BAD: "How do I write a transform skill?"
GOOD: "I would like to create a proc that will act as a transformation.
This would include...
changing the icon,
adding a special /obj/hud/aura overlay,
outputting to everyone in view "[src.name] has turned SSJ!".
It would also increase their powerlevel variable times 10.
Thanks!"
The most part, don't be a help vampire. Try to look at the DM Reference (http://www.byond.com/docs/ref/) and Resources before coming to the forum for help.
If your having trouble starting, I'd suggest checking out some classic demos such YourFirstWorld as well as the DM Guide.
There's a difference between skimming over things, and actually reading it. The best way to learn is do some of the examples in the guide, as well as tweaking YourFirstWorld.
I do not recommend using this AI demo because, judging from the code itself, the author doesn't know what he's doing. The code is lazily slapped together into one .dm file. He claims the AI code is optimal and doesn't take much CPU, however that itself is mostly bullshit. Here's why:
When an AI in his demo executes New(), it begins a loop that checks for players in the vicinity. If a player is in the vicinity the AI will perform any actions in that loop, it will skip to the next increment after a routine sleep(). This is not at all any different from having AIs autonomously behave regardless of player presence.
A better way to have done this would be to "activate" AIs every time a player moves to a square close to an AI. This way you don't have potentially hundreds of pointless loops going on in the background, wasting processing power on things that could've been used for more important things.
tl;dr: Don't use this demo. Use this one instead. It's far more organized and structured in a way that makes it easy to read and study.
I'm guessing your looking for something around a A.I
http://www.byond.com/developer/Rifthaven/A.I.Code
is the one i used and i just learned and built off it to make the NPC's / Aka Monsters do moves instead of just bumps.
Hope this is what your looking for.