An RTS or something else? This will help people give you a list of what you need to learn.

I was thinking more along the lines of making something somewhat similar to the sims 3.

As you might imagine getting content for your project can be one of the hardest thing for a programmer, so have you looked into getting content? Have you looked into what format your (lets say) 3d models will be in? This way you can find a library or start coding a loader for them yourself.

I've been thinking of using Maya for that, as I'm more familiar with how to use Autodesk suites than other 3D modelling suites.

Surely its hard,but maybe not so hard as it seems. There are many open source engine available,such as ogre for mmo.sdl for mobile. glm for math etc.And fmod is now free for indies,its a simple and elegant audio lib/

Btw,i am on the way making my own game,its extremely fun.

If I were you, I would work off some already existing code that someone is completely cool with you using as a base. You learn way faster and get more done quicker.

Sorry for not paying attention to this thread as much as I should be, I've been moving.

http://www.gamedev.net/topic/75762-annotated-objects-which-drive-behavior/
That's a thread on a technique used in the Sims for AI, I think it has a link to a paper on the technique.
For pathfinding I always liked this link to start out.
http://www-cs-students.stanford.edu/~amitp/gameprog.html

AI and game logic is what you'll definitely have to implement yourself. You're most probably fine with using an engine or libraries for everything else.

Thank you so much for this, this is definitely helpful, I shall bookmark all those links at once.

And I'll look into the engine and libraries more to see what will fit best with what I need.

fmod is now free for indies,its a simple and elegant audio lib/

glm for math

I shall also look into these libraries, thanks!