I'm quite late here, but I like using a variant of 4d6 drop lowest. You do the typical first roll, adding any 3 of those dice, then you flip over every die, and keep 3 of those. Repeat two more times for a total of 3 rolls and 6 stats.
Since opposite faces add to 7, a high stat on one side will usually correspond with a low stat on the other side. Because of the drop lowest, it's possible to get high stats that don't have an equally low counterpart (a roll of 6, 6, 6, 1 would give 18 and 8, as opposed to the 18 and 3 that 3d6 would give with this method).
I especially like this method because it keeps the randomness without risking a bunch of negatives or all stats above 13. It's also possible to get Standard Array and the 12, 12, 12, 13, 13, 13 array with this method.