There’s nothing like doing!
The best way to be a good TA – to be able to really help your artists – is to be enough of a working artist yourself that you can see things through their eyes. That means you need to make stuff (models, animations, effects – you’ll probably have to pick one and stick with it for a while to get useful experience) and most importantly you need to push it all the way to completion.
You don’t have to be a great fine artist – life drawing classes or acting classes are great, but not essential – however you really need to live with some assets from concept through completion, with all the bumps along the road that usually entails: redesigns, bugs, changes of purpose and all the other random stuff that happens in every production. It’s really important to have a goal in sight and push towards the goal, with other people giving you feedback and critiques and all the usual back and forth of doing production art. Without that it’s hard to understand the role of iteration and exploration in art. The cardinal sin of all tools programmers is failing to see that “an efficient description of the finished product” is never the same as “a good system for chasing after the finished product in your head”.
If you can do it, convince your bosses to let you work as a part-time artist for a while. Long enough to really live the life. You’ll probably get the grunt work, and you need to be ready for the usual artistic ego issues. However being a good artist (at least, on a team) is all about learning to live with feedback anyway – it’s a bit rough on the self-image at first but if you can stick it out you’ll really see what your users go through every day. Plus you’ll get a much better sense of what is broken and needs fixing.
Over the long haul it’s great to get experience in all of the big divisions (modelling, environments, animation, and effects) but each one is an art form of its own. Plan on spending a good chunk of time on each.
It’s a ton of work on top of your regular job But it will make you better, incomparably better, at your job over the long haul.
Plus, it’s fun.