Altering Die Rolls
When I am starting up a new group of characters, I usually have them roll 4d6, 7 times, take the best six, and assign each number to a stat and have them choose a race with ability mods and class.
First, I calculate the point buy value of each character's stats. I then take the lowest stat of the lowest point buy character and raise it, until it is no longer the lowest point buy character. If two stats are tied, I take the primary stat used for bonus spells for the class, else I start with Strength and move down on the character sheet. If the character was really rolled low, this sometimes gives the punted stat a really good boost, sometimes, somewhat higher than 18. Personally, I think this is okay for the worst rolled character in the party in a non-primary stat, otherwise why would you assign your lowest stat there?
Then, I take the highest point buy character and lower the highest stat by 1. If two stats are tied, I take the primary stat used for bonus spells for the class, else I start with Strength and move down on the character sheet. This usually makes the "superman roll" less optimized in his primary class ability, but still have the best all around stats.
I then take the new lowest point buy character, and raise the highest stat by 1 until it the character is no longer the lowest point buy character, but not higher than 18. If the highest stat is 18, I raise the second highest stat instead.
Next, I take the highest point buy character, which may be the same as before, but may not be, and lower the highest stat by 1. If two stats are tied, I take the primary stat used for bonus spells for the class, else I start with Strength and move down on the character sheet.
Then, I then take the new lowest point buy character, and raise their lowest stat by 1 until they are no longer the lowest point buy character.
Finally, I take the new highest point buy character, and lower the lowest stat by 1.
When I do this with players I usually allow them to roll their dice, and then I write down my dice alteration steps in envelopes, and open them 1 step at a time, so that it is known that I'm not picking on anyone specifically.
For example, Initial Dice rolls for a sample party of four before alteration give:
Human Cleric: S:16, D:13, C:13, I:12, W:17, Ch:16. Point Buy:47.
Halfling Rogue: S:9, D:20, C:12, I:13, W:11, Ch:7. Point Buy: 36.
Dwarven Fighter: S:15, D:13, C:17, I:11, W:11. Ch:7. Point Buy: 31.
Human Wizard: S:8, Dex:13, C:14, Int:16, W:10, Cha:7. Point Buy 22.
After alteration they become:
Human Cleric: S:16, D:13, C:13, I:11, W:15, Ch:16. Point Buy:41.
Halfling Rogue: S:9, D:20, C:12, I:13, W:11, Ch:7. Point Buy: 36.
Dwarven Fighter: S:15, D:13, C:18, I:11, W:11. Ch:7. Point Buy: 34.
Human Wizard: S:16, D:13, C:14, I:16, W:10, Ch:10. Point Buy 35.
What I like about this method, is often the lowest point buy character has the highest single stat of the group, and the highest point buy character has the lowest high stat of the group.