Pick one of the following ability score arrays–
The heroic array: 15, 14, 13, 12, 11, 10. This array differs from the standard array in that your lowest scores are still average, rather than below average. Player Characters are exceptional people, and thus ability scores represent that.
Strength and weakness array: 16, 14, 13, 12, 10, 8. This array models the deficit score of the standard array, but increases the strongest ability from 15 to 16. It creates a little more variety in terms of ability score modifiers or allows for a character with an ability weakness.
Both arrays add up to a 30-point buy method (for comparison, the standard arrays is based on a 27-point buy method), with the exception that the core rules do not allow starting ability scores above 15 (before racial adjustments). Both arrays are mathematically superior to what you could expect from rolling 4d6 drop the lowest.