A reminder that anyone fasting may not eat until tzeis hakochavim–even on a Friday fast.
And then Kiddush must be made–Vayechulu and both berachos.
And then one must wash–or at least eat mezonos.
Someone cooking for Shabbos may taste the food (only a little bit) and then spit it out.
One may take a hot shower today, since it is erev Shabbos.
One who eats by mistake must continue fasting.
One who forgot that it is a fast day, and made a berachah, took the food item, and then remembered–this is a major shaylah.
Halachah lemaaseh—eat a minimal amount.
One should not spend a fast day waiting for it to be over,but must use it for inspiration and contemplation.Asara B’Teves is a perfect time to be mekabel on oneself not to talk in Shul–talking desecrates the kedusha of the Shul or Beis Medrash–our Mikdash Me’at.