After you finish your lecture, it can be tempting to kick back and relax.  Or if you have another class after the one you finished, you may be rushing to get to your next class.  But when you do that, you're losing an opportunity to reduce your studying time.

After class, the best thing to do is to immediately review your notes.  This is because the material is fresh in your head.  You're able to quickly understand the material and help get it into your long-term memory.

But when you wait until later to review your notes, such as when you get home, it'll take longer to understand the material.  You'll need to spend some time trying to refresh your memory on what was taught in class.

It's better to save your time from doing that and take advantage of the opportunity to review your notes immediately after class.  Even if you have to go straight to your next class, spending just 2 or 3 minutes reviewing your notes is still beneficial.

If you establish this as a habit, you'll save a lot of time.  For instance, let's say it takes you 15 minutes to refresh your memory when you review your notes at home.  You have 3 classes a week for this one course.  So that's 45 minutes a week, 180 minutes a month, or 540 minutes per semester (assuming that final exams start in the fourth month).  You'll be losing 9 hours per semester.

If you take 3 courses, that's 27 hours lost.  With 5 courses, that's 45 hours lost.

But if you establish the habit of reviewing your notes immediately after class, you'll be saving those hours.