Thank you!
I actually don't know. There's a section for player submitted stuff on the Daybreak forums where the senior art director hangs out and provides tips for creators. They also require you to post your contributions there for evaluations prior to actual submission apparently.
If you're still a student then you can get a one year license for basically any program from Autodesk for free. On the condition of non-commercial educational use. That's where I started.
As for how you get better, or even find out how to begin. I would look for sites that provide learning material. Youtube has decent beginner tutorials for interfaces and building your first stuff. Lynda is all right. Plurasight/DigitalTutors is great.
Don't be afraid to reach out to more experienced people. I was incredibly lucky in my case. I looked up one of the players that had gotten items accepted for TF2. Contacted him and asked for help. Incredibly enough he accepted me and began to mentor me.
Start out small. It can be tempting to start out with a massive project, like a tank. But it won't go anywhere productive in 90% of cases. Grab a simple object close to you and try to recreate it in your program of choice. A cup, a plate, a lighter, a bottle. Easy to break down things. This will help you get a better feel for the tools in your toolbox, hone your abilities to identify challenges, and find solutions.
Practices, practice, and more practise. That's all I can say. I can tell you from personal experience that it sucks to sit there and make crap that look god awful, all the while getting frustrated at ones inability to make a simple thing. But, there's just no cheat to git gud. Sooner or later you will find yourself getting better.
Depending on what kind of 3D you want to do. Then there are a lot of different ways to do it. For example I'm trying to get into character modelling and soft surface. So I've been toying with Zbrush and a tablet for about a year now. If you want to do weapons, vehicles, or general hard surface modelling. Then look up 3DSMax, or Maya.
Those are my tips and experiences. Use them as you see fit.
Thanks! I was looking into some detailing on the back. Just can't decide on what would fit.
Thank you, kinds lads. I appreciate it!