Making sure you hit often with melee touch attacks?

[Diminutive Titan]

I was wondering what is the best way to hit with touch attacks,

Let's say you're a full spellcaster, how high would you have your Strength ability score to hit with touch attacks often? How does touch AC scale with monsters?

Could you also skip out on Strength ability investments and take Weapon Finesse for touch attacks? Does that work?

I thought I read somewhere that touch attacks are considered light armed attacks... but the ruling on this is vague and confusing.
Need a little help here.

[Wrong John Silver]

Touch attacks are considered unarmed attacks, and so can be finessed, like light weapons.

So, since Dexterity is a defensive ability score, while Strength is pretty much only offensive, then you definitely can get Weapon Finesse, skimp on Strength, and use Dex instead. Heck, don't forget to take Reach Spell, too, and use Dex both for ranged and melee touch attacks.

[Kydeem de'Morcaine]

Reach spell or the Spectral Hand spell to touch from far away (much safer) are excellent choices.

[David knott 242]

Also, big monsters have lousy touch ACs. Hitting them with touch AC attacks is normally not a challenge at all. The problem, of course, is that you have to get right next to them to use a melee touch attack. It is definitely better if you can manage a ranged touch attack.

[Wrong John Silver]

The one alternate choice is being an Aberrant Sorcerer, use Long Limbs for your reach, and then sticking with Strength for melee touch attacks.

[Imbicatus]

Or just snag Long Limbs from Eltritch Heritage. You could also gain reach from either being a white haired witch or being a normal witch or hexcrafter with the prehensile hair hex.

[Gregory Connolly]

Be an Eldritch Knight and have a high BAB works too.

[Kydeem de'Morcaine]

I think I'll stick with spectral hand and be at the other end of the hall. :-)

[Lincoln Hills]

The best way to hit with touch attacks is to have your meaty weapon-using friends bull-rush them into a low spot to give you +1, knock them prone to give you +4, and stand on the opposite side of them to give you +2. (Stunning and blinding effects optional, but pleasant).

The next-best way is to cast true strike.