You know what I mean by stair steps. You'll see them on shoulder shaping, and on sleeve caps - anywhere you cast off a number of stitches on successive rows.
Like this. Familiar, yes? Stair steps.
We are all very used to seeing this. It isn't the easiest thing in the world to deal with when you are seaming the sleeve cap - it would be much better if the whole thing were smoothed out into a nice neat slope, and there weren't any actual steps at all.
So, how about this instead?
Much better. Achieving this smoothing effect is very, very easy indeed. (And yes, I know you could use short row shaping, but this is simpler, and unlike short-row shaping you don't have to think about it at all until you actually get to the cast-off - or more precisely, the very last stitch before the cast-off.)
So, on the row before you are going to work a cast-off - don't work the last stitch. Instead, slip it purlwise.
Then, turn your work. Don't work the first stitch - that's the one you just slipped - instead, slip it purlwise again.
and don't work the second stitch either. Slip that one purlwise as well.
So now you have two stitches on your RH needle, and you are supposed to be casting off here. So treat those two stitches exactly as if you had worked them in the usual way - lift the first stitch over the second one, and drop it off the end of the RH needle.
One stitch cast off.
And then, just carry on with the rest of that block of casting off, working the other stitches and casting them off exactly as normal. When you come to your next block of casting off, treat it in exactly the same way. If it is at the beginning of a purl row, it makes no difference, you still slip those stitches purlwise.
You'll be surprised at the difference that this trick can make - this combination of slipped stitches at the beginning of each little section smooths out that step very nicely.
Just one thing I should add - you don't usually need to use this trick right at the beginning of a cast off sequence. For instance, if you are working a shoulder cast-off - a sharp corner right there at the beginning is not a problem. I'm using it here at the beginning of a row only because this is partway through the shaping of the sleeve head for a set-in sleeve, and I want to smooth the transition between the section worked with decreases and the section worked with casting off.