I would recommend waiting until October to begin outlining; you really wont' have covered enough your first semester to understand how the big picture fits together, nor even what belongs in the big picture.
Outlining is not done to gain understanding of the general concepts, really. It's more to understand how the details come together to form a body of law (e.g. how the concepts of offer, acceptance, consideration, promissory estoppel, breach, etc. form one body of law - contracts, and how to apply that body of law to a fact pattern and determine whether a contract exists, what the terms of that contract are, and whether that contract has been breached, and how much damage that breach has caused). Until you cover one or two sections of a class, you won't really see how this stuff fits together.
As for how to do it, everyone does it a bit differently. You should look through the outlines you've received from 2 and 3Ls to see how they've done it, what sort of information they included, how they organized it, etc. I'm sure your section leaders will go over much of the same.
Once you've gone through this once, you can start outlining whenever you want in the following semesters. As a 3L, I still prefer to wait until early October to start, but some people decide to start after the first week of class. It's one of those "whatever works for you" things.