Unable to find a manual for an old Sony KV-C2569D, I figured out myself how to program the channels. Because this took me quite some time understanding the RM-816 remote control (it’s harder than programming Java or even assembler!), I will give some pointers.
The RC actually has two sides, one simple side that has the day-to-day buttons, and one side for when you want to do more than switching channels or turning up the volume (or, for what I read, to impress your guests). To change from one to the other, press the buttons at the top left and right of the RC and pull the RC out of it’s casing. Note that the programming buttons are at the bottom of the ‘advanced’ side, but they are hidden if the RC is all the way in it’s casing!

For every channel you want to program, do the following:
You can cancel your actions if you haven’t saved it yet, using the diamond with arrow button.
If you want to move a channel, select it and do steps 1, 2, 5.
If you want to delete or remove a channel, so that it will not be shown when you browse through all your channels, press the diamond with arrow, press the C00 button, and press the diamond to save.
It has been decided. I will create a blog where I can share some useful bits of information or thoughts that I just want to throw out into the world.
— Oliver