I'm building simple storage boxes for the house which will be nailed and glued at rabbeted corners. I tried a few different ways to cut them and settled on the following because it was relatively fast, accurate, and allowed me to play with a variety of hand tools.
First, I scored deep lines with my slicing gauge, outlining the section of wood that needed to be removed. The deep line created a crisp starting point for the shoulders on the inside and outside of the rabbet.
I shaved a shallow trench along the scored lines with my plow plane. This channel provided a guide for my crosscut saw.
I sawed the near and far corners of the rabbet to final depth and then, tipping the handle up a bit, I used the front few teeth of the saw to cut the inside shoulder of the rabbet. I leveled the saw for the last few passes until I reached the final depth.
I found that, rather than taking full passes with the saw from the very beginning, angling the handle up made it easier to steer the saw and keep the teeth close to the shoulder.
The saw kerf provided a nice stop cut for the next move. Working from the edge of the board toward the stop cut, I used a chisel and mallet to remove most of the waste.
When I was very close to the scored line on the edge of the board, I cleaned up the rabbet with a shoulder plane.
This method worked very well, but if you don't have a plow plane to cut the channel for your handsaw, you can clamp a board to your workpiece to use as a saw guide, or you can remove a sliver of wood by sliding a chisel along the scored line.
If you don't have a shoulder plane for the final passes, you can finish the entire cut with a chisel if you're careful.
As another alternative, you just might happen to remember—after you've cut all the joinery—that you own a really nice moving fillester plane with skewed blade and nicker which would make quick work of the same task.