It really depends on what you are playing.
For many classes - Ranger, Rogue, Monk, Paladin - something like 14, 14, 14, 12, 12, 10 is a very good choice. If you have a way to get advantages from all of your stats, then getting the most total +'s is desirable. You can play classes like Cleric, Druid, and Barbarian with these stats too, though you rarely see it done.
For other classes - notably Wizard and Fighter - you can get a big boost by specializing, so you will see a few 18, 14, 10, 10, 10, 8's or even 18, 14, 12, 10, 8, 8 (fighter dumbs int and cha, wizard dumps str and cha). You see alot of large weapon Barbarians built like this too, to maximize that damage bonus, but frankly I think it is a waste of Barbarians nice skill set to do so. But that will depend on your DM and how often you make skill checks in your campaign.
For most spell casting classes, and frequently Rogues, you'll see something in the middle like - 16, 14, 12, 12, 10, 10 or 16, 14, 14, 12, 10, 8. I'd probably build a Cleric, Bard, Druid, or Sorcerer along these lines.
However, it is an important point that you don't have to be 'optimally' twinked to be a survivable and interesting character. It is perfectly fine to build a fighter or barbarian with a 14, 14, 14, 12, 12, 10 stat set, or a have rouge or cleric built with 18, 14, 10, 10, 10, 10. There is nothing wrong with a fighter with 14 in wisdom and only a 10 in dexterity. There is nothing wrong with a rogue with Int as his highest stat, or a barbarian with 14 charisma. There are all sorts of ways to play the game that don't involve smackdowns, provided you and your DM are both willing to focus on something other than creating smackdown characters and sending them against each other.