Part of staking involves pruning back axillary suckers -- so if you are just staking/caging and otherwise leaving the tomato plants to grow at will, then not much will give a really satisfying non-jungle-y result
Pinch out the little branchlets that start to grow from where each leaf attaches to the main stem. (there are different schools of thought as to whether there should be just 1 main stem or >1, which has consequences for how the tomato is supported). You can do this every week or 10 days when you go out to tie the new growth to the stake.
If you are going to pinch them back to 1 or a couple main stems (and you have to keep doing this all summer), then anything works ok -- a stout 2x2 stake, a T-post, even a long piece of rebar although I find it less secure than the previous two methods. Pound whatever it is WELL into the ground, like 2+ feet depending on your soil and the tomato variety. Use a sledgehammer (wear goggles if sledgehammering on metal); you will prolly have to start by standing on a stepstool or low stepladder if you plan to have a tall (like 5-6') stake.
There are also those spiral stakes. I have heard them recommended but never tried them due to their price. My understanding is that you're supposed to not have to tie the tomato to them much or at all.
If you really like cages, put T-post *stoutly* into the ground (again, like 2+ feet) for each tomato plant and make your own cage by bending a length of 4x4 welded wire mesh fence or 'field fence' (page wire, whatever it's called in your area -- bigger holes) into a cylinder. Do the math before buying the fencing -- it takes a lot more length of it than you might expect
STRONGLY secure the cage to the stake. My parents use this method (although mom also does pinch back the suckers) and it works really well for them.
If you are not going to pinch them back but just let them form their own happy little tomato jungle, I would recommend planting them EXTRA EXTRA far apart. I saw someone tie them to a trellis of 4x4 welded wire fence supported on t-posts once. Personally though in years when I'm not going to do the maintenance thing I just let them sprawl. Yeah, you lose a bit of the fruit to rot and voles... but my thinking is that this is a fair price to pay for the privelege of being lazy about things
Good luck,
Pat
I can never sink them deep enough into the soil to provide decent support. I'd like to build something (translation: ask my husband to build something 
) better this year. 
