Its the same as any other prayer, nothing special needs to be read.
You perform it in 2's and 2's up to 12.
Best time is the last part of night, just before you do your sehri .
Prophet has a hadees that make Witr your last prayer and many scholars recommend that the night you have niyat for tahajjud, dont pray witr after isha and pray it after tahajjud.
3 rakaat witr does not replace Tahajjud.
i prayed tahajjud between 2:30-3:00 am is that ok? sheri starts at about 3:30/4:00...