Depending on what stage of incubation it's in. You will see veins at around 5-7days. First I would candle it. In early stages, you will see nice pronounce veins if it's good. If bad...the veins will be bit blury or see blood clots like.(I cant find the word to describe lol) So sounds similar to reptiles.
If egg looks good..then candle again a few days latter to see if still good. If bad, just toss it. Should turn atleast 3X's a day.
If egg is in latter stage, then it will be obvious when candled.
You need temp at ~101degrees in an incubator without fan and around 99.5 in an incubator with fan. I know some reptile bators are preset and doesnt go that high but that's the temp you need.
As far as when it will hatch...we would need to identify the egg as to what type of quail. Some info that may help is what area you from. Or a picture. Description of candle. Im guessing it may be Valley or Gamble since I havent heard of too many Coturnix makin it in the wild.
Read more here:
http://www.thatquailplace.com/smf/index.php?topic=3656.0 and the other sticky at the top. Good luck.