Depends on subject.
I'm a History student so we have a very specific format to it; we call it PEEL, or Point - Explanation - Evidence - Link.
We start with a brief intro, a bit like an abstract, about what we're gonna talk about. Then we take the most important factors in favour of our view and write about them first, using the info in the question. Then the opposite, weigh them up and make a judgment.
With historical sources the tricky part comes in understanding how much you can glean from one statement; for example we had a source talking about women in war camps during wartime Nazi Germany. On the surface it looked normal until I picked up the camp was in Germany, when they generally didn't keep camps there but in conquered territory (usually Poland). That sort of thing.
Then you just see how you can tie your own knowledge to the source info to create a cohesive, strong and innovative argument.