This is a must for every handicapper to know.  If you notice here on vegasinsider.com they have bet percentages there on moneyline, spread and OVER/UNDER for each sport.  They have what the line for the game opened at and what the current line is at.

What to look for is: for instance the Heat open at -7 for the game and there is 74% of the betting market on them but the line went from -7 to -6 with only 26% of the bets coming in on the other team you have to wonder why did the line move the opposite way?  Well there is sharp money and there is public money.  Since the Heat are a public team they are almost always bet on by the public that`s why there is 74% of the betting market on them.  So with the line moving to -6 there is sharp money moving that line which tells you that they know something the public doesn`t.  This is a tell we use to make our moves everyday and this is an excellent strategy to profit from over time.  This is an absolute must to research before you make your wager.