What it takes for a person sleeping normal, non-magical sleep to wake up?
I believe that wounding them wakes them immediately, end even in sleep they are allowed to make Perception checks (although with a Penalty) and if they sense danger they can wake up? But would being affected by an effect that does not cause hit point damage, but requires a save would wake them up (especially if they succeed the save)? Few examples I'd like to consider: charm person spell, wisdom drain touch (like the one that lamias have), scrying spell, detect thoughts spell, long lasting poison taking effect.
As far as the rules are concerned I don't think there's anything to guide here.
As for how I'd run it, anything happening around a sleeping person will give them a perception check to notice, though with the -20 penalty for being asleep (that's somewhere in the rules). For spells and effects that impact the individual, I would first ask what kind of impact? If the person were awake, but blind and deaf would they be aware of what's happening and in what way? Targeted spells cause a save that can alert the target, so I would allow a perception check (still with penalty). Scrying spell, no perception check, although the sensor that is created by scrying can be detected by perception (still applying sleeping penalty). Poison, I imagine causes an amount of physical pain and might wake someone up without any checks at all. Probably depends on the exact nature of the poison.