couple of more things I have noticied and beleive me I have only been paying attention to this for about a week. It does seem like the favorite goes up alot more than the dog goes down (esp in west coast games). Another thing I have sort of seen happen is in mid afternoon if line is 3-4 pts off opener it seems to bounce back toward the opening number(unless injury involved), so I try and get the low # and feel it has maybe bottomed out.
I also do the math in EVERY poetential middle and reduced juice makes all the difference in the world if this a good middle or not.