/lit/ - Literature

Are there any tips on how to make characters sound different during dialogue?
I have a story that revolves around a fairly large cast. Essentially half of them are soldiers, and half are politicians. There are a few others here and there, but I'm not worried about them.
Politicians should be a little easier because one is just opposing the other a lot of the time, but the soldiers have me stumped. Especially because maybe half of the dialogue so far takes place during battle scenes so it's little more than shouting orders and soldiers doing their specific jobs.
Any specific tips on how to do those?

I want to find some way of making money doing writing as an undergrad in university. I'm gonna be spending most of my summers working in a research lab but the hours aren't exactly a full time job, and I'd like to be able to do something from just my computer, though I don't really know what kind of writing to get into. Science articles for newspapers or journals? I don't know.