You have to guess what public might do, and when/if any steam might come in. Sometimes these two clash, steam might like a side BECAUSE they think public will bet against it.
It isn't scientific.
For regular games the lines are hot at around 1100 Am East time to about 12, then again a a couple hours before game time.
So that is the best time to monitor. The rule is, if you see one place jump, get the number at another place you have before they follow suit, and they almost always do.
I was already wrong once this morning as I bought Chi Sox before they bottomed out, but that is the nature of the beast, WHEN is the best time, and when will you get min and max level.
If we could all do it 100% of the time then the books wouldn't offer bases anymore.