Having a passion is a good start, it will help keep you motivated as you learn and get better. Going to a school or university is probably the best way to learn 3d but if you're like me and can't afford it, tutorials are a BIG help.
I don't know what your skill level is but for starters, I would recommend going to Simply Maya's Video Training Section and doing the free tutorials. They are basic and will help get you started. As you do the tutorials, show us your work in the forums so we can see how you are doing and so people can give you help along the way.
Once you have some basic knowledge, I'd recommend purchasing the more in depth tutorials. They will help you take your skills to the next level. Basically, the more you work with Maya, the better you will get. But tutorials are an EXCELLENT way to learn. Just don't forget to show us your work as you do stuff because even though you'll learn alot from the tutorials, you can learn just as much from getting feedback from all of us here at Simply Maya.
Don't be satisfied with what you can do but rather strive to do the things you can't do!