So you've got a blob of unpunctuated text in front of you that you didn't even write and you have to make sense of it. Good luck. Read through it once sans punctuation then make sense of it by subordinating and coordinating all of the grammatical goodness within. If you're not so great with punctuation and you still haven't done anything about it, check out this site: Grammar Book and then if you want some entertainment, check out this little ditty on semicolons:The Oatmeal.
This punctuation extravaganza should only take 10-15 minutes. The rest of the time is free for you to use however you need to use it (eh, hem, for this class).