Some quotations from text books about stereo mixing, that I found important:

Beware of phase cancellation
Be cautious when panning similar elements hard left and right, as it can potentially cause phase cancellation when played back in mono or through certain playback systems.
If you notice any phase cancellation issues or an imbalance when checking the mix in mono, consider adjusting the panning positions or using stereo widening techniques sparingly.

Each musical style has its unique requirements for delay effects. Delays often add fullness to vocals or lead guitar parts in rock and pop. Electronic and dance music frequently employs rhythmic delays to create pulsating effects that align with the beat.

Genre Delay Time Feedback Wet/Dry Typical Use
Rock/Pop 100-300 ms Low to Medium 20-40% Enhancing vocals and lead guitar parts
Electro/Dance Synced to Tempo Medium 30-50% Creating rhythmic patterns and pulsating effects
Reggae/Dub 300-600 ms High 40-60% Creating spaced-out rhythmic patterns and atmospheres
Ambient 500 ms – 2 s Very High 50-70% Producing ethereal, wide soundscapes
Jazz/Blues 200-400 ms Low to Medium 20-35% Adding depth to solos and improvisations
Hip-Hop/Rap 150-250 ms Medium 25-45% Enhancing rhythmic elements and vocal chops
Country 100-200 ms Low 15-30% Subtle echoes on vocals and string instruments
Classical 600 ms – 1.5 s Low to Medium 10-30% Creating a sense of space and grandeur
Metal 100-250 ms Medium to High 30-50% Thickening riffs and solos

Typical Delay Mistakes To Avoid
While using delay, it’s essential to be aware of common pitfalls. Overusing delay can clutter a mix, making it muddy and indistinct. Setting delay times without considering the track’s tempo can result in a disjointed rhythm.
Neglecting the wet/dry mix balance might bury the effect or overpower the original signal. Being mindful of these common mistakes helps craft a more polished and professional-sounding mix.

One fundamental approach is using delay on vocals to add depth without cluttering the mix.
Set a moderate delay time and low feedback to create a subtle echo that enhances vocal tracks.

Combining delay with reverb can produce rich, spacious soundscapes. The trick is to balance the two effects to enhance rather than compete with each other. Adjusting the wet/dry mix and the timing of each effect is crucial for a harmonious blend.