Moon situation for Shawwal in 2006 at Houston TX:
Oct 21st, Moon is already set before Sunset at 6:49 pm. No chances of sighting.
Oct 22nd, Moon is almost about to set right after Sunset at 6:48 pm and too close to Sunlight. No chances of sighting.
Moon situation at 7:07 pm on Oct 23rd. High chances of sighting.
Bukhari Volume 3, Book 31, Number 133: Narrated Abu Huraira: The Prophet or Abu-l-Qasim said, "Start fasting on seeing the crescent (of Ramadan), and give up fasting on seeing the crescent (of Shawwal), and if the sky is overcast (and you cannot see it), complete thirty days of Sha'ban."