Legal writing can seem very mysterious, but it really boils down to a basic formula:
state the legal issue/point/question you’re going to discuss;
give the Rule (or Rules, including all relevant definitions) for that issue;
Apply the facts from the hypothetical or real fact pattern to those Rules;

This is usually called “IRAC” for Issue, Rule, Application, and Conclusion. (The “A” can also be called Analysis; I prefer Application because that more clearly describes what you do in that part—Apply the law to the facts.) It’s also called CRAC because the Issue need not be stated in the traditional format—“The issue is whether the defendant is liable when [relevant facts plus law]”—but can also be stated as the conclusion—“The defendant here is liable because s/he [relevant facts plus law].” So long as you’ve pointed out where you’re going in the discussion, the “I” is satisfied. Think of it as the turn signal of legal writing—just as in driving, you make others confused and angry when you turn without signaling. These are not emotions you want to evoke in professors (or supervisors or clients).

The Rule is usually not too troublesome for students, but they often leave out necessary definitions and/or start to mix in facts before fully stating the general Rules. The point of the statement of the Rule for the reader depends on the reader, of course: for a professor, it shows you’ve memorized the relevant Rules; for the supervisor, it reminds her of the Rules that she may not have really thought about since law school; for the client (yes, someday you’ll have clients!) it starts to give him important information on which he’ll base his decision on how to proceed. No matter which audience you’re writing for, they all need a clear statement of the law as a general Rule before they start thinking about how their facts may be put together with that Rule.
For example, a Rule statement when contract formation is at issue would be, “Contract formation requires offer, acceptance and consideration,” not, “Bob formed a contract with Sue if his statement was an offer, Sue accepted it and there was consideration for their agreement.” The Rule is for all contracting parties, not just Bob and Sue. Also, mixing law and facts usually leads to a sentence more like, “Bob formed a contract with Sue because he made an offer, Sue accepted it and there was consideration present.” A professor will write “conclusory” next to this because all I did was state that the Rules were met—I didn’t show how or why they were met in that sentence nor did I set myself up to do that discussion as I did with the “if” in the first version. If I continued on and actually applied the Rule to the facts, then my grade would still be okay because I would have done an Application, but I would not get as good a grade as the student who showed that she knew the Rule because she wrote it as a Rule, and that she understood the Rule because she went on an Applied it in the next section.
As for defining all terms, if I stop after stating the Rule—whether generally or with facts—and start using the facts with the Rules, then the reader still doesn’t know what I mean by any of those terms. (Of course your professor knows, but she needs to know that you know what you mean!) You have to first define what constitutes an offer (“an offer requires…”), an acceptance (“the offeree can show acceptance by…”) and consideration (“consideration is…”). Usually that takes at least one sentence per legal term. Only then can you Apply those Rules to the facts.

I’ve called this posting “The Case of the Missing ‘A’” because that is where most students get into trouble and you definitely cannot get an A grade without an Application. Most students fail to fully Apply every bit of the Rules they worked so hard to memorize to the facts that the professor (or the supervisor or client) worked so hard to create (or share). This is where the most points on a law school exam can be found (and is the reason the supervisor gave you the assignment or the client hired you) because it is your opinion on how this specific fact pattern works with the general Rule. We use Application in our daily lives—we just usually short-hand that discussion. You want to give a long, considered discussion on an exam or an assignment. Think of a time you made a major decision and you told a close friend about it. You may have explained your reasoning fairly quickly, and without a complete explanation of your reasoning because your close friend/family member would know your considerations and what you’d rate as a pro or a con or prioritize. That is, you had Rules (morals, standards, considerations) that helped you reach your decision and your friend would know and understand those quickly as you applied them to your situation.
For example, say you needed to buy a new car—you’d have to consider the amount of money you could spend, the number of miles you’ll regularly drive, and how environmentally conscious you are. You might say to your friend, “I’ve decided on a hybrid because I can get extra hours at my job this month.” Your friend would know you previously didn’t have much money to spend but that you really care about being environmentally conscious, you drive a lot of miles so need good gas mileage, you have a car to trade in, and “extra hours” means overtime for which you get time-and-a-half pay. So you didn’t fully explain your monetary considerations and you didn’t even mention the non-monetary considerations. Now imagine you’re having that same discussion with a stranger who has to understand exactly why you made that decision—you’d have to think a lot more and explain a lot more about why and how you came to your decision. “Although money has tight, I will be able to get more hours at my job this month for which I will receive time-and-a-half pay. That pay for the month should be enough for me to afford a down-payment of $2,000. I also have a car I can trade in which I expect to get me a $500 credit. Therefore, altogether I can make a down-payment of $2,500 which would make my monthly payments only $150. I know can afford to pay $150 per month because my current payment is $200 per month.” Look how many sentences that took, and you haven’t even explained your feelings about the environment or how the number the miles you drive impacts your choice.
The professor needs to read that reasoning because otherwise he cannot know that you have an actual working knowledge of the Rules and how they Apply to facts. The supervisor and client need to read or hear that reasoning because that is why they have hired you—to get your legal opinion on factual situations. Anyone can just memorize legal Rules; it is the person who learns to think like a lawyer who can use those Rules with facts and write that Application in a clear and reasoned way. On most law school exams, showing that you memorized Rules is likely to get you no better than a C grade; Applying them thoroughly can get you an A.

The Conclusion rarely gets people into trouble when they remember to do one. Just in one sentence answer the issue you raised in your first sentence and end. If you feel you need to further discuss the reasons behind your Conclusion, you didn’t solve the case of the missing “A”—you didn’t Apply enough and need to go back to that part and further explain your thoughts (if you’re hand-writing an exam, just start a new paragraph and write, “It should also be noted that…” and keep going).

I hope you all solve the case and get an A!