stringbean said:
I have a character in my campaign who is a Rog1/Rgr1. His typical tactics go like this:
round 1: Move to cover then Hide, if possible.
round 2: Fire at unsuspecting opponent, doing Sneak damage in most cases.
round 3: Lather, rinse, repeat.
My question is this: At what point does he "Blow his cover" (become a viable target) and necessitate another Hide roll?
I dunno if he needs to "re-stealth" after every shot, wait for someone to actually "Spot" him (would they get bonuses to see him after he attacks?) or if he needs to spend an action to make another Hide roll ....
Sorry for the silly question, I'm sure y'all can straighten me out in no time. 
First of all, notice that getting a COVER and HIDING are two separate and very different thing.
Behind a cover, he gets benefit to AC and ST, and that's it by the rules, which means he can shoot from behind the cover (unless of course it's total cover) without problems. Let's assume for simplicity he's not trying to get advantage from crouching or dropping to the floor every time, ok? That kind of trick could "increase" the degree of cover but has nothing to do with Hide.
Hide has the purpose exactly to hide from view, behind something which will eventually provide a cover, so that it is difficult to know where you are. Once you make yourself visible, for example shooting, they know where you are, even if you are behind the cover.
What your PC is trying to do, as it seems to me, is using Hide to get the advantage of being invisible, therefore the Sneak Attack, which is not true. At the very most, if he had been hiding before the combat started, he might have surprised the target when he did the first shoot (i.e. get to shoot in the surprise round), but I don't think it would be by itself enough to grant a Sneak Attack.
Notice this:
If people are observing the character, even casually, the character can't hide. The character can run around a corner or something so that the character is out of sight and then hide, but the others then know at least where the character went. If the character's observers are momentarily distracted (as by a Bluff check; see below), though, the character can attempt to hide. While the others turn their attention from the character, the character can attempt a Hide check if the character can get to a hiding place of some kind. (As a general guideline, the hiding place has to be within 1 foot per rank the character has in Hide.) This check, however, is at –10 because the character has to move fast.
There is no real point in hiding after every shoot behind the same cover, because it's not this the point of the hide skill, which is rather to reach a place unnoticed so that the enemies don't know where you have gone. In your case they still know where you are, you are not invisible at all, and all you get is your cover bonus.
Another matter again is when you are in poor illumination: the rules are very vague an undefined, and it seems that 3.5e will address the case in good details, but before that they don't help.
