Q:

What are the criteria for wins, losses, and saves in MLB?

I've read the rules for determining Wins, Losses and Saves for pitchers, and I've never been able to make heads or tails of it.  Is there an easier way to explain it?

A:

The verbiage is a little thick on these rules, so maybe some examples will help:

The winning pitcher is defined as the pitcher who last pitched prior to the half-inning when the winning team took the lead for the last time.
a. Exception 1, the starting pitcher must pitch at least 5 innings to be eligible for a win.
b. Exception 2, if a relief pitcher, who would normally be in line for a win, makes a "brief appearance" and is deemed ineffective, the official scorer can grant the win to the succeeding relief pitcher.

Example #1:  The Cardinals are playing The Cubs in STL.  The Cards bat in the bottom of each inning.  The score is 0-0 until the bottom of the 7th inning in which the Cardinals score a run.  The game ends with the score 1-0.  The Cardinals pitcher that pitched the top half of the 7th inning would be the winning pitcher of record.
Example #1a:  The Cardinals are playing the Cubs in STL.  At the end of 4 innings, the Cardinals are winning 9-8 in a slugfest.  The Cardinals swap out their starting pitcher with a long reliever and end up winning 9-8.  The Long Reliever would be the winning pitcher of record.
Example #1b:  The Cardinals are playing the Cubs in STL.  At the end of 6 innings, the score is 0-0.  In the top half of the 7th, with 2 outs, the Cardinals insert a reliever, he throws one pitch to get the final out.  In the bottom half, the Cardinals score a run.  In the top half of the 8th, the Cardinals insert a new reliever who pitches all of the 8th inning.  The Cardinals win 1-0.  The Official Scorer could decide that the reliever who pitched the 8th inning is the winning pitcher of record.  

The losing pitcher is the pitcher who allows the go-ahead run to reach base for a lead that the winning team never relinquishes.  Note:  A starting pitcher does not have to pitch 5 innings to qualify for the loss.

Example #2: The Cardinals are playing the Cubs in STL.  In the bottom of the 6th inning, with the score 1-1, the Cardinals hit a home run.  They win the game with the score of 2-1.  The Cubs pitcher who gave up the Home Run is the Losing Pitcher of record.
Example #2a: The Cardinals are playing the Cubs in STL.  In the bottom of the 6th inning, with the score 1-1, the Cubs pitcher gives up a Double.  The Cubs replace that pitcher.  The new pitcher gives up a Single and the running on 2nd scores.  The game ends with the score 2-1.  The Cubs pitcher that gave up the Double would be the Losing Pitcher of record.
Example #2b:  The Cardinals are playing the Cubs in STL.  The Cards score 7 runs in the first inning and the Cubs starter is lifted after only getting 1 out.  The Cards eventually win 7-2.  The Cubs starting pitcher is the Losing Pitcher of record.

Saves are awarded to a pitcher if
a. He finishes the game for his team.
b. His team wins.
c. He is not the winning pitcher.
d. He has logged at least one out.
e. He meets one of the following:  

Enters the game with a lead of no more than three runs and pitches at least one full inning.  
Enters the game with the potential tying run on base, at bat or on deck.  
Pitches at least 3 innings.

Example #3:  The Cardinals are playing the Cubs in STL.  The Cards have the lead in the top of the ninth by a score of 1-0.  The Cards bring in a relief pitcher and he strikes out the side.  That reliever would be awarded the save.
Example #3a:  The Cardinals are playing the Cubs in STL. The Cards have the lead in the top of the ninth by a score of 5-0.  The Cards bring in a relief pitcher and he strikes out the side.  No save is awarded.

A:

The pitcher of record can be determined as follows:

If the starter for the winning team goes 5+ innings and leaves with a lead that is not relinquished he is the winning pitcher
If the starter for the losing team leaves without the lead and his team does not regain it or tie, he is the loser.
If the starter leaves with the lead, but does not pitch 5 innings, and his team maintains the lead, the scorekeeper assigns the win to the "most effective reliever" (score keeper's discretion)
If a team gains the lead after the starter leaves and maintains that lead, the win is assigned to the current reliever.
If a team loses the lead after the start has been removed and does not regain it, the loss is assigned to the current pitcher (even if he is not charged with the runs).

Saves are a bit more complicated. The rules are as follows (no starter may get a save)

A pitcher who enters with the lead and pitches at least the final 9 outs gets a save.
A pitcher who enters the game with a 3 or fewer run lead and finishes the game
A pitcher who enters the game with the tying run on base, at-bat or on deck and finishes the game with the lead.

