From the little i know of psychology, i know that the dreams that people have dream during REM (or Rapid Eye Movement) sleep. REM sleep generally occurs at the start and end of the sleep cycle, and the most vivid dreams come at the end (i think) of your sleep cycle where REM sleep is most "vivid". If the sleep cycle is interrupted before this final period of REM sleep then dream will not have occurred yet (this happens is people are awakened by alarm clocks and get insufficient sleep).
Now, since i finished high school a week ago i have the privilege of sleeping without an alarm clock, and i can say for certain that i am having dreams which i can remember when i wake up a lot more often. During school i would only get 5 or 6 hours of sleep whereas now i get more then 8 and i'm finding it wonderful.
It feels really good when you can wake up and think, "Oh Yeah, I Actually Remember That!" And my dreams seem more realistic just before i wake up, i have woken up a few times confused as to why i'm in a bed and just generally disoriented.
If I remember to write down one of my dreams in detail, i'll be sure to post it here!
