I was recently wondering if I am saying the bracha on my tallit katan at the right time (I'm not married and don't wear a tallit gadol). When should the bracha on the tallit katan be said? Before it is put on? After you are fully dressed? At the beginning of davening?
The blessing is said immediately before putting on the Talit Katan. Code of Jewish Law Siman 9:8:
Regarding all mitzvos, one recites the blessing upon the mitzvah preceding its performance. This means that the blessing should be made prior to carrying out the mitzvah and immediately after one recites the blessing, one must do the mitzvah, without any interruption at all.
In a case where one puts it on when he can't recite the blessing (at night, or his hands are unclean), he says the blessing when he can. Code of Jewish Law Siman 9:9:
If he dons the Talit Katan at a time when he cannot recite the blessing on it, then afterward, when it is day and his hands are clean, he should take the tzitzis strings in hand and recite the blessing.
Also one should put on the Talit Katan and say the blessing only when he's not naked. Code of Jewish Law Siman 5:17:
If one's heart can "see" his own ervah (private parts), even if the ervah is covered as when he is wearing an unbelted robe, it is forbidden for him to recite any sacred texts. Rather, he must wear pants that are snug or a belt around his waist or but his arms on the robe across his body so as to separate between his heart and his ervah.