QUOTE(Bitter @ Nov 8 2007, 11:39 PM)

Sinilar topic: Can someone write a comprehensive list of rules for when to put the tallis over your head? It seems like everyone always knows except me.
(That's why Lubavitchers have mashpia's and mentors).
It's a good question and we all see people with all sorts of different practices even in one shul [minhag hamakom notwithstanding since minhag hamakom has no relevance to anyone other than that girls have to wear socks].
First of all, as far as I understand, there's a range of opinions. Take the Mishnah Berurah for example. He cites the Ba'ch that it's laudable to cover one's head from the beginning of davening till the end. Wonderful. That makes it laudable but not obligatory, so seemingly one can opt as one sees fit and as one is personally comfortable. But according to the MB is it obligatory at all? Leaving aside the claim that there's an obligation for a double head covering [which I believe there is not, an oblique reference in the Beit Yoseph to OC 8 notwithstanding; I believe it's a chassidic chiddush, but we've discussed this lots of times previously], according to the MB is there any obligation to cover one's head with a tallit? The Shulchan Aruch says it's "nachon", or correct, at the beginning of OC 8, but the context of that statement is davka when donning a tallit right before the berachah in order to fulfill atifah. Arguably, the SA is not speaking of any time after you finish donning the tallit any more than the SA would hold it's laudable to remain with the tallit covering one's mouth as one must [ke-derech ha-yishma'eilim] when one is donning the tallit. In other words, according to the SA, as understood by the MB, it's only laudable according to the SA to cover one's head with a tallit while donning the tallit, since that's clearly the context, and then the MB goes on to say that it's actually laudable to cover one's head throughout tefillah. But obligatory? No way.
A nafka mina would be if one needs to say a new berachah on the tallit, a second time. According to the above understanding, one could say a berachah, and don the tallit, without doing the whole atifah thing with covering one's head and covering one's mouth, and so understands some commentators.
So one way of understanding it is that it's laudable to cover one's head when donning the tallit, but not obligatory according to the SA, but it is obviously normative practice to do so. But after that? A range of opinions and practices. As I said above, according to the Bach, it's laudable throughout davening, but certainly not obligatory. In fact, I would argue that there are times when one davka should not. After all, if the reason for covering your head with a tallit is humility [hachna'a], then being the only person doing so in a shul where nobody else is would seem to me, in my opinion, to be attracting, and yuhara, and the opposite of humbling, and the opposite of what one should be trying to accomplish. On the other hand, the flip side of the argument is that if one's personal minhag is to cover one's head throughout tefillah, regardless of what others are doing in shul, one should do so at all times without prejudice.
But what do people actually do? We've all seen people do different things. In my shul, some don't cover their heads at all after they don the tallit, some cover from the beginning of tefillah till the end, some cover just for the amidah or just when they get an aliyah, a range of personal practices. But what I observe to be the most common practice in my shul is to cover one's head from Barechu till after the amidah. What's the source for this and why do people do that? People probably do it because they see others doing it. But what's the source? I have no idea. But it seems to me to be consistent with one of the opinions in Mesechet Sofrim. Contrary to the rhetoric of the OPS, it's not so clear that there is any obligation to cover one's head with a kippah at all times, but there is a clear obligation, sourced in one of two opinions in mesechet sofrim, to cover one's head for shema and the amidah. So in my opinion, covering one's head with a tallit during shema and the amida [ie from barechu] is consistent with that opinion in mesechet sofrim, if one considers a kippah to be an inadequate covering.