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<p>Often.</p>
<p>More seriously, it’s best to read the relevant chapter(s) before lecture - you’ll have a much better sense of what’s going if you do; there’s a reason professors give you syllabi. It’s harder than you’d expect to find a few hours every day (or even just once a week) and simply read a textbook, but it’s worth it.</p>
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<p>Varies. Looking through old exams is very helpful, as is taking practice exams professors may provide. Reading through your notes, making flashcards, putting together some sort of study guide, etc. - all the things you may have heard about in HS but didn’t have to do because the classes were easier 
- can all be good ways of doing things. (I found that making a study guide was especially helpful for 18.02, where lots of things turn out to be related in cool ways if you take the time to examine carefully. Case in point: Stokes’ Theorem.)</p>