Using a decision correctly requires separating what was decided from what was said.
Procedural posture first. What was appealed, from what ruling, and under what standard of review. A statement made in reviewing a dismissal on the pleadings assumes the allegations are true and says nothing about the evidence.
The holding. The proposition necessary to the result on the facts presented. Everything else is dictum — persuasive at most, and not binding.
The facts that mattered. Which facts the court relied on, and whether they are present in your case. A decision applying a standard to particular facts may be distinguishable rather than controlling.
Concurrences and dissents. A concurrence necessary to the majority may limit the holding. A dissent identifies the strongest counterargument and often predicts the next development.
Subsequent history. Whether it was affirmed, reversed, vacated, superseded, or overruled in part. Citing a reversed decision is the single most damaging research error.
Later treatment. How other courts have read it — followed, distinguished, criticised — which is frequently more informative than the opinion.
Publication status and the citation rules that govern it.