By now you might be reconsidering your choice to go to law school. Don't worry, this is normal; I was doing the same thing last year. Keep in mind you are learning how to read all over again.
Below are some tips on how to brief cases:
1) Start with the Issue. This is the purpose of the case. Look for the magic word "whether." If the opinion doesn't include it, look for clues in the case book such as section or chapter headings that can help you figure out what the case is about and why you are reading it [besides that it was assigned :-)]. This is the most important thing to get right, because you will use it as the lens that you examine the rest of the opinion through because all the important bits of the opinion serve to answer this question.
2) Next find the holding. This is going to be the answer to the "whether" question, and will be a sentence or two about what the Court held. Go beyond just saying "affirmed" or "reversed." You want the actual rule they came up with.
3) After you get the holding find the reasoning. This is the why of the opinion. If you can, try to figure out what the losing side's reasons were as you will get a better understanding of why the Court sided the way it did. This will probably be a combination of synthesis of existing rules and application of the facts.
4) Now start recording the facts. You only really need to pay attention to the facts that were used in the reasoning, and in some cases, none of the facts may have been used because the Court was examining a wider issue of law.
5) Finally find the procedural history, basically how did this case get to the Court which wrote the opinion. In a pinch, it's enough to know what Court wrote the opinion (i.e. Court of Appeals, Supreme Court), and the jurisdiction (i.e. is this a state or federal opinion, does it deal with state or federal law).
Finally, I would say its worth writing your case briefs out until they become easy to do because once they become easy, you probably are comfortable navigating an opinion. Then its fine to switch to book briefing.
Be well folks.