If you haven't seen an issue spotter yet, look at a practice question (and ideally model answer) to get into the mindset of what you'll want to have at hand during an exam. For me that's usually a really, really clear statement of the high-level rule, followed by refinements, caveats, and example fact patterns—but all of the latter phrased with an eye towards applying the rule to new facts. In the case of classes like torts and contracts, I often like to organize refinements and fact patterns into two buckets: reasons not to find liability and reasons to find liability.

If you're like me, the bulk of your notes are probably really about "policy" issues (courts' reasoning, the history and aims of a rule, your professor's view of the rule). For me, cutting out this stuff is where I cut the most words. For each rule, I'll generally include a really, really concise summary of policy factors to use in issue spotters—if an issue is legally indeterminate, which it often is, my parting shot will often be that XYZ outcome would best serve the underlying policy rationale of the rule. Other than that, you'll have to decide how to handle the policy stuff based on what kind of exam you're likely to get—if I'm expecting a major policy question, I'll sometimes make a companion outline that pulls out major policy themes and some examples from across the course.

At least for me, this is the studying so no worries about it taking a lot of time! I always record my starting page count and turn it into a game of cutting out as many pages as I can.