I don't know much about using delay, like what kind of delay to use when playing lead or rhythm delays. When to use slapback delay or what kind of delay to use for clean mellow arpeggio playing. Got any words for the unwise delaywise?
Fractions of a second is a good place to start. Get to know your times.
10-60 milliseconds (ms) is barely perceptible, and the "mix" of delay and dry is fairly even.
60-150ms slapback delay --only one echo is heard (this knob is called feedback or regeneration--at minimum on the knob you only hear one slap)
150-250 short delay --now you may want to pull back the mix of the delay signal. Also you want to turn up the feedback and hear it fill out more.
250-500 can be rhythmic and spacious. Spacey. Most "analog delays" this is maximum they can go.
500-800+ms is pretty much either a dramatic effect (like "Dazed and Confused" or "Brighton Rock") or mixed more subtly and longer repeats is simulating playing in a cathedral or digital loop. Think "Janes Addiction" This is Digital delay.
Different delays sound darker or brighter and offer different mix or feel. Many people debate the controls--are they complicated, do they move the time smoothly, or chop it up. Programmability vs. set-it-and-forget-it.
I like a simple 3-knob unit that works the time smoothly when you turn the dial. Loopers are cool, too.
All I ever use is a little slapback delay, as described above, to make my rhythm playing stand out a bit. Reverb seems to do the opposite: makes the sound recede somehow. Can't speak to the use of longer delay times.