Importing 5e ritual casting

[frogglesmash]

As the title suggests, I want to import ritual casting into 3.P. To that end, what do people think would be a good rule of thumb for determining which spells should and shouldn't be available for ritual casting?

[TotallyNotEvil]

Maybe how little Sorcerers pick it up but also how often they carry it around as a scroll?

[stack]

Things that have notable material costs that prevent them from being overused. Things that have a use outside of combat (damage evocations don't make good rituals). Really, anything that having it as a ritual won't open easy abuse. What that means will depend on your table.

Due to the way spells are prepped in 5e, a niche ritual spell taking up a prep slot is a larger cost that a mid level caster prepping it in a low level slot in 3.5.

[liquidformat]

3.5 already has Incantations (http://www.d20srd.org/srd/variant/magic/incantations.htm) and Spheres of power has Rituals (http://spheresofpower.wikidot.com/rituals)

[Psyren]

3.5 already has Incantations (http://www.d20srd.org/srd/variant/magic/incantations.htm) and Spheres of power has Rituals (http://spheresofpower.wikidot.com/rituals)

Base Pathfinder also has Occult Rituals. (https://www.d20pfsrd.com/alternative-rule-systems/occult-adventures/occult-rules/occult-rituals/)

[Elvensilver]

For deciding which spells should be ritual-castable, look at spells that can be made permanent. Those are already tested for being not game breaking if being cast often.
If ritual spells are being usable by not (high-)level magic users, look mostly for quality of life improvements, that last at least an hour (if you're static while casting, you can't expect the problem to stay near), or options to gather information.

[Faily]

For deciding which spells should be ritual-castable, look at spells that can be made permanent. Those are already tested for being not game breaking if being cast often.
If ritual spells are being usable by not (high-)level magic users, look mostly for quality of life improvements, that last at least an hour (if you're static while casting, you can't expect the problem to stay near), or options to gather information.

Spells with long casting time (Sending, Scrying, etc) would work for that.
As do Spells with expensive components and focuses as Stack mentioned.