A follower and patron who coaches high school boys basketball recently sent an email about the Four Factors made famous by Dean Oliver in his book Basketball On Paper. Below is my response:
More than anything the four factors comes down to winning the factor(s) over your opponents. Teams that win and win big with gaudy W-L records not only win factors, but create lots of margin between their factors and their opponents. For example, our eFG% is really high (good offense), and our opponents’ is really low (good defense). 
Let’s take a stab at each factor as far as goals go. 
High School boys, get it above 50%. That equates to 1.0 PPP (points per possession). But again, the goal is to win the factor and create margin. So if you are not a great offensive team, you can still win by being a really good defensive team (keeping your opponent’s EFG% low or lower than yours.) But really good High School boys offenses are north of 50% for efg%. 
Same deal, create margin. Yours low, theirs high. Some really good boys teams are able to keep TO% in the mid-teens. Shoot for below 20% – but the lower the better. Would be nice to drive your opponent’s TO% higher and higher to create that margin. If you employ a defensive style that does not generate many opponent TOs, then taking care of the ball becomes imperative as you do not want to be negative in TO% margin. 
EFG% and TO% are like 1a and 1b when it comes to W-L correlation. Win those two factors and you’ll rarely lose. 
If you are a team that intends to pursue Offensive Rebounds aggressively, aim to rebound at least a third of your misses. This would be an OREB% of 33.3% or greater. Therefore, we’d like our opponents’ DREB% to be 67% or less because they rebound the misses we don’t gather. We’d love our DREB% to be 100%! But that’s not realistic. Drive your DREB% as high as you can. Again, margin. We want to shoot better and shoot more than our opponent. If you don’t intend to really pursue OREBs it makes your DREB% that much more vital.
The “fourth” factor in terms of correlation to W-L. But still vital! Same, create margin. Live on the line and keep your opponents off the line. Hard to say what a good goal would be, for I work with some great teams with a low FTR and some bad ones with a pretty high FTR. Not as tightly correlated as the other factors. But shoot for 0.30 or higher. The lower the better for opponents. 
Hope this helps! Basketball is not a very complicated game. Teams win when they take the ball from their opponent without the opponent scoring (i.e. grab defensive rebounds and force turnovers), keep the ball away from their opponent (i.e. avoid turning the ball over and grab offensive rebounds), and convert possessions into points by shooting efficiently from the field and converting from the free throw line.