[Glice]

Depends on what you want from 'detuning'. Urusei Yatsura used to be quite happy for it to slip out of tune mid-song. And there's plenty of people who use inappropriate string gauges for the timbral affect it has. The only proper piece of advice is that tuning up should be done with caution - going more than a tone or so up will warp the neck if you're using thicker strings, so it's worth going to a higher string or thinner gauge. Also, it's always important when detuning to tune to below the note, then wind upwards to the object note, because it'll be more stable then. And leaving a lot of slack string that coils around the nut, above and below the entry point, is important too, and the string is more supported, and putting less strain on the neck (this is true of standard tuning as well).