First off, dandwiki has a bad reputation. I'm not sure who this is with, but I'd personally suggest using d20srd instead.
Here's their excerpt on Incorporeal Creatures (as a subtype):
Incorporeal Subtype
An incorporeal creature has no physical body. It can be harmed only by
other incorporeal creatures, magic weapons or creatures that strike as
magic weapons, and spells, spell-like abilities, or supernatural
abilities. It is immune to all nonmagical attack forms. Even when hit
by spells or magic weapons, it has a 50% chance to ignore any damage
from a corporeal source (except for positive energy, negative energy,
force effects such as magic missile, or attacks made with ghost touch
weapons). Although it is not a magical attack, holy water can affect
incorporeal undead, but a hit with holy water has a 50% chance of not
affecting an incorporeal creature.
So let's quick break this down with a list of things that ignore incorporeality:
- Magic weapons
- Creatures that strike as magic weapons (including sufficiently leveled monks)
- Spells, spell-like abilities, or supernatural abilities.
Of these, there is a 50% chance to ignore corporeally sourced damage (such as fire), but will always take damage from positive energy, negative energy, force effects, or things that explicitly target incorporeal targets.
So the answer is: You can always hit with anything (as normal), but you may not harm the incorporeal target.
However, if you are doing the appropriate types of damage, you will always do damage, while other spells may not-this is entirely dependent on the spell in question. Cure light Wounds? You're set. Burning hands? Flip a coin.
Yes
You can ready a free, move, or standard action. That action can be to cast a spell that has one of those casting times. If that spell is also a ranged attack (which can be a ranged touch attack, a type of ranged attack), you can meet the requirements of the feat Deadeye Shot (PH2 78).
The DM may require the trigger for your ready action to be very specific, however, forcing the caster to predetermine target, spell, and maybe even target's square, depending on how strictly he interprets the ready action.
The DM may balk at such a task because the feat Deadeye Shot seems to assume a ranged weapon instead of a spell, but nothing in the feat's text mandates that. A manticore could use the feat with its tail spikes just fine, for instance.
If the DM continues to resist, point him to the Weaponlike Spells section of Complete Arcane, which says, in part, that
Any spell that requires an attack roll and deals damage functions as a weapon in certain respects, whether the spell deals normal hit point damage, nonlethal damage, ability damage, or energy drain. Such spells can threaten critical hits, can be used in sneak attacks, and can be used with favored enemy damage bonuses. You can even use a number
of combat-enhancing feats to... improve the effectiveness of weaponlike spells... (85)
Best Answer
Probably, in the case of spells with a range of Touch.
From the SRD on Touch Spells:
A handshake is a form of a touch, so go for it. The main question is whether or not a "charge" from a touch spell or the effect of discharging such a spell is visible.
Maybe in the case of ranged spells used as a Ranged Touch Attack.
Compare the description of Chill Touch:
To Ray of Enfeeblement:
Ranged Touch Attacks by and large work like Ray of Enfeeblement: A laser-beam or other thing not affected by armor attacks your target.
The DM could rule that a beam that originates from your hand is guaranteed to strike someone you're shaking hands with... But they could just as easily argue that the beam originates from the tip of your index finger and goes flying off into nowhere, or that the target's hand isn't a direct enough hit for the spell to take effect.
Other Ranged Touch Attack spells may have different descriptions, making them easier or harder to perform against someone you're shaking hands with.
The issue here is one of language. Ranged Touch Attacks are not "touch" from a description standpoint ("attacks like touching someone, but from an arbitrary distance"), they are "touch" from a mechanical one ("attacks that bypass armor in the same way as the touch attack mechanic").
One last note: If the person shaking your hand perceives you spellcasting (say, because you don't have the feats to hide Verbal and Somatic components), I would rule that they could drop the handshake as a reaction to your spell casting unless you had something special stopping them (Bigby's Crushing Handshake?).