what you do is entirely up to you and you also have to find the period of time that works best for you. I was up for about 45 minutes, which is the time it took me to watch an episode of Smallville or Supernatural.
I did go to sleep with the intention to lucid dream, but i just found that after WBTB my mind is a lot more awake in a dream, meaning that i notice those wtf moments when i am dreaming.
Since I wake up several times a night, I have no need of setting an alarm clock, but they usually say you shuld wake up some 5 or 6 hrs after going to sleep.
My ideology in general would abolish the usage of concentration, but that's just me, since i've also found that i cannot force control while lucid, but believing makes it real.
Don't try to bend the spoon. That is impossible. Instead realize that there is no spoon and that it is you that bends.
(but it would help if you did something in connection with lucid dreams)