How do the sportsbooks make the spreads??

When I say that I want to know what stats do they actually use and what algorithm do they use to compute to get the line

I ALWAYS wondered this but what got the ball rolling was a guy I met on twitter

I noticed one day he put a line up for an nfl game up a few days before the books did..

It was week 3 .. he was talking about a week 4 spread.. I also noticed he liked college softball.. so I decided to follow him because I'm a huge softball fan

So softball season comes and we started sharing picks and what not. One day I asked him what he thought a spread would be for a game the next day... He sends me spreads for games the next 7 days.. he even has if PITCHER A STARTS this will be the line but if PITCHER B STARTS this will be the line..as the week went on I check them out... He's nailing then!! Juice and all

So yesterday I asked him how to show me how to do it...

And no response....

SoftballsRandy

It is a bit more complicated than this but the spread is supposed to be where it will generate an equal amount of action on both sides. So when you bet on a sport where the lines are posted a week before like football I believe it is best to research the games and find a line your work says is off. Confirm injuries and suspensions and if all is good bet it as quick as possible. 

I know many people think it is best to wait until just before a game. I feel like on a bad line it only gives the book more time to adjust it closer to be correct.