That's tough to tell who's getting to the game first. Common misconception (IMO) is that the "sharps" bet the line down (or up) before the public gets to it. I know it was a real old school thing for Vegas to allow certain players to play the lines before they are hung for the public, but there are so many outs for players now, mainly online....therefore it's really not as if someone is getting to the line before any Joe. Pros and Joes, w/the advent of online gambling, seem to now have equal stake. Another example, and I look to pro foots again, because around 6:30-7 on Sunday if I'm still sober enough, I'll line the following weeks games. Do this for a while, and you'll get a pretty good handle on where the action may or may not be. I marked the Pats as a 3.5 choice over Miami, and early line at pinny was 3. This was quickly hammered to 3.5. This is not to say I'm an oddsmaker, but the 3 was available, and to move off of that generally took lopsided action. This is going to sound like I'm contradicting myself, but in steam bets, the line goes one way, til the Pros feel they've gotten a good enough price, then hammer the other side.
Ex...just an ex, $$$ is not even a guestamite
Opener NEW ENGLAND -3.
50K bet on NE -3 (pro/public $$), 10K on Miami +3(Pro/public)
Line NE -3.5
(remember, all speculation here)
Public starts pounding the pats
Pros bet miami at +3.5
Public continues to bet the pats.
Pros end up getting off the 3, and have little invested to buy the hook. when playing for their kind of $$$, paying small 10s of 1000s for a hook is nothing....
Still, very hard to interpret line moves. Especially in pro sports.
Maybe that clears it up, maybe it makes it even more difficult to understand.
gl nonetheless