For DoTs, the bonus is multiplied by a certain figure (depending on the spell), added to the overall damage of the DoT then divided equally among the ticks.
Say there was a DoT that ticked 10 times for 10 damage and had a multiplier of 100% (normal). If you had 100 Spell Damage, the overall spell would gain 100 damage (10 ticks adding up to 200, as opposed to 100). Then that 10 on each tick of the DoT would be 20 damage.
Specific types of Spell Damage only apply to that type of spell (Immolate won't be effected by items "... of Shadow Wrath").
Nukes get put through the multiplier, but since they only tick once, it adds the full damage after that. (so a Shadow Bolt for 8K will get +
86 with 100 more spell damage, since the multiplier is 86.71, so it'll hit for 8086)
Oooh, lookie, found a site! Click here for coefficients (multipliers)! I got there eventually =P Edited, Oct 26th 2007 9:14am by ecirphsoj