How to Annotate Lecture Slides Before, During, and After Class

Lecture slides are usually an outline, not a complete explanation. Copying every bullet gives you a second copy of the deck; waiting until exam week leaves you guessing which examples, warnings, and connections the lecturer added aloud.

A better system gives each slide three passes: preview before class, capture meaning during class, and convert gaps into study prompts after class. The result is an annotated source you can use without rewriting the whole presentation.

Set up a small annotation key

Use five marks consistently. Put the key on the first page of every deck.

Mark	Meaning	What to write
!	Lecturer emphasis	Why it matters or how it may be assessed
+	Added explanation	The point that was spoken but absent from the slide
EX	Example	The case, calculation, or analogy used in class
?	Gap	The exact question you need to resolve
↔	Connection	Link to a reading, earlier lecture, formula, or assignment

Avoid a complicated color system that requires constant decisions. One symbol plus a short note is enough.

Before class: preview, do not pre-study everything

The Carnegie Mellon University lecture-note guide recommends checking the syllabus topic, previewing the assigned material, and reviewing the previous lecture before class. Use that advice to prepare the deck in about ten minutes:

1. Read the title and learning objectives.
2. Scan section headings and repeated terms.
3. Put a question mark beside unfamiliar vocabulary, formulas, or unlabeled visuals.
4. Add one connection to the previous lecture.
5. Leave space beside dense or important slides.

Do not write full explanations yet. The purpose of previewing is to create places for new information to attach during class.

During class: record what the slide cannot tell you

The Barnard College note-taking guide suggests reviewing slides in advance and writing directly on them when they are available. It also emphasizes listening for meaning rather than trying to capture every word.

Prioritize five kinds of spoken information:

• the lecturer's explanation of a bullet;
• an example or worked step;
• a contrast between two similar ideas;
• an exception, warning, or limitation;
• a clue about assessment or expected terminology.

If you miss a point, leave a question mark and a blank space. Do not stop listening while you reconstruct a sentence from memory.

A teaching example

This is a fictional teaching example, not a real lecture or product output.

Suppose a slide says only:

Sampling vs assignment

During class, the lecturer explains that sampling concerns who enters the study, while assignment concerns which group participants enter. Your annotation might be:

• + Sampling → population to sample
• + Assignment → sample to groups
• EX Survey volunteers, then randomly assign volunteers to two study conditions
• ? Which step affects generalizability, and which affects causal inference?
• ↔ Week 2 research-design diagram

The slide remains the anchor, while your notes preserve the meaning that was spoken around it.

After class: run a fifteen-minute repair pass

CMU recommends reviewing notes soon after the lecture, explaining ideas in your own words, and marking unclear material. Use a short repair pass rather than rewriting the entire deck.

1. Resolve easy gaps

Use the assigned reading, course glossary, or official recording to fill straightforward blanks. Add the source or page number. If you cannot verify a point, keep the question mark.

2. Write one takeaway per section

At each section break, add a sentence that answers: “What should I now be able to explain or do?” This prevents a long deck from becoming one undifferentiated list.

3. Create questions from the annotations

Turn emphasis, examples, and gaps into prompts:

• Explain the difference between X and Y.
• Apply the rule to a new case.
• Recreate the diagram with labels hidden.
• Solve the example with one value changed.
• State the limitation the lecturer emphasized.

4. Schedule unresolved questions

Move genuine gaps to one small list for office hours, a tutorial, or the next class. “Review slide 24” is vague; “Why does this model exclude variable Z?” is actionable.

Use AI without inventing the missing lecture

Notoo's slides-to-notes workflow accepts PPT, PPTX, and PDF lecture decks and can organize readable material into notes, flashcards, quizzes, and mind maps. Its current page also warns that slides may omit spoken explanations and that diagrams, formulas, tiny labels, and image-heavy slides need checking.

Use it for structure and follow-up practice, not for pretending that sparse bullets contain a complete lecture. A useful prompt is:

Organize the readable slide text into sections. Preserve course terminology and slide references. Mark unexplained diagrams, formulas, examples, and transitions as gaps. Do not invent what the lecturer may have said.

Compare the draft with the deck and your class annotations. Add spoken examples only from your own notes or a recording you are permitted to use.

A reusable slide-annotation template

Copy this block into your notes for each lecture:

Lecture: [topic and date]

Before class

• Previous-topic connection:
• Three unfamiliar terms:
• One prediction about the lecture's main question:

During class

• ! Emphasized idea:
• • Added explanation:
• EX Worked example:
• ? Unresolved question:
• ↔ Course connection:

After class

• One-sentence section takeaways:
• Two closed-book questions:
• One diagram or problem to recreate:
• Question for lecturer, tutor, or reading:

Adapt the method by course type

STEM lectures

Capture the reason for each step, not only the final equation. Annotate units, assumptions, signs, and the point at which an example changes from general rule to special case. Redraw one diagram or solve one variation after class.

Humanities and social sciences

Mark claims, evidence, counterarguments, theorists, and connections to assigned texts. When the lecturer interprets a quotation or case, write the reasoning, not just the conclusion.

Language-heavy courses

Keep exact technical vocabulary beside a clear-English paraphrase. For international students, add a translation only after checking that it preserves the course meaning. Record pronunciation or stress only when it helps you participate or present.

What not to do

• Do not highlight nearly every bullet.
• Do not copy the deck into a second document before class.
• Do not treat an AI expansion as something the lecturer actually said.
• Do not delete question marks just to make the notes look complete.
• Do not postpone all review until the exam period.
• Do not upload restricted course material without permission.

FAQ

Should I print lecture slides or annotate them digitally?

Either can work. Choose the format that lets you listen, add short notes beside the correct slide, and find your questions afterward. Course rules and accessibility needs matter more than the device.

What if the lecturer uploads slides after class?

Take a lightweight outline during class and leave slide-number placeholders. When the deck arrives, attach only the notes that add explanation, examples, emphasis, or questions.

Should I make separate notes from the slides?

Only when the deck is hard to navigate or you need a cross-lecture study guide. First annotate the source; then extract section takeaways and retrieval questions. Avoid rewriting unchanged bullets.

Can AI fill in what the lecturer probably meant?

It can explain general background, but it cannot reliably recover a missing course-specific explanation. Mark the gap and verify it with the lecturer, reading, official recording, or another approved source.

Make the next deck active

Preview one upcoming lecture deck, add the five-symbol key, and write one question before class. After class, spend fifteen minutes repairing gaps and answering two prompts without looking. For a structured draft you can verify and turn into practice, upload the deck to Notoo.