I've been reading up about exposing to the right as the preferred shooting technique and had a question about the practicalities of this. Am I right in assuming you don't know if the highlights have been blown until after the image is taken and you check the histogram? If so is there a lot of checking and deleting because a channel has been clipped or because it's not as close to the clipping threshold as it could be. Or, after a while do you develop a feel for how much to expose to the right, getting non-clipped shots most of the time?
Yep, you are right that you don't know until after the fact, and yes, I look at the (RGB, not luminance) histogram primarily to determine that. I find that in most situations, autoexposure gives me something "pretty good", and that I'll tend to "shoot, glance at histogram, move on", and when that doesn't work it's more "shoot, glance at histogram, quickly sketch in some exposure compensation, shoot again, glance at histogram, move on".
I don't delete in the field. My shooting style tries to keep my brain as much as possible aimed at "seeing", and less time (but not less than necessary) on "intellectual thinking".
How much? It depends a little, but if I think the highlights will be visible in the histogram (this can be tricky when you only have a couple tiny highlights in a darker scene, but that's a rarer case), I tend to aim to put them about, oh, I dunno, an tenth of the visual width of the histogram from the right hand side.
A lot of times I will accept a capture with wider spacing if I know that the exposure I eventually want in the print is darker or about the same as the exposure I captured, I'll worry about ETTR more if I feel like I'm going to pull up the shadows, or if my histogram has pegged or nearly-pegged shadows I'd like some level of detail in.
This all sounds like a lot of work, but it becomes, for me, very intuitive and quick after a while.