I generally use the standard PHB method of 4d6, drop the lowest die & arrange as desired.
I once used a Rifts-inspired variant: 2d6+6 in order and +1d6 if original score was a 16, 17 or 18. This method allowed some extraordianry abilities without cherry-picking (most of my players will put their highest stat in Dex every time since it affects AC, ranged attacks (very important in a campaign with guns), Ref saves & many skills--the strategist even tried to back to 1e order (S, I, W, D, C, Ch) so that his high INT roll could be used for DEX!). I'm looking for a high-powered variant like that for another game I'm dreaming of. I am also toying with the idea of 2d4+10, in order.