Perhaps 252 HP, 120 Defense, 136 Sp Attack. This gives you good bulk and the special attack EVs allow you to attack after some Calm Minds.
I always push this for a Lugia set: Roost/Recover, Ice Beam, Reflect, Calm Mind
Item: Lum Berry
The Lum Berry prevents random freezing, which is really the only thing that used to be able to take down Lugia.
Roost/Recover are great, you can just heal up any damage you take while setting up Calm Mind. Roost is used with Pressure, while Recover is used with the more prefered Multi-Scale, which makes Lugia next to invincible. Recover is used because Roost cannot be used with Multi-Scale, being a Gen IV move.
Reflect is the way to raise Lugia's Defense. 6oo something defense is enough to take a hit from anything.
Calm Mind raises Lugia's Sp Def and Special Attack. After a few of these, Lugia can take any special hit and KO any foe. You can heal off any damage done during set-up.
Ice Beam is Lugia's best source of attack. Ice Beam gets super-effective hits on most of Ubers. It has god PP, unlike Aeroblast. And Toxic doesn't work because Steel or Poison types would then completely wall Lugia.