The Basics

Diakonos uses all the common GUI shortcuts, so you already know many of them right off the bat:

Open a file             Ctrl-O
Save                    Ctrl-S
Close a file            Ctrl-W
Create a new buffer     Ctrl-N
Quit                    Ctrl-Q
Copy the selected text  Ctrl-C
Cut the selected text   Ctrl-X
Paste                   Ctrl-V
Find                    Ctrl-F
Find and replace        Ctrl-R
Find again              F3
Undo                    Ctrl-Z
Redo                    Ctrl-Y
Help                    F1
Next word               Ctrl-right or Alt-right
Previous word           Ctrl-left or Alt-left

Some other basic functions:

Configure Diakonos      F12
Begin selecting text    Ctrl-space
Stop selecting text     Alt-U
Save buffer as          Alt-Shift-S
Clear match highlights  Ctrl-Alt-U
Smart indent            Tab
Switch to buffers       Alt-1, Alt-2, etc. Alt-0 0 for 10
List buffers            Ctrl-Alt-B

Also supported is selecting text by holding down shift and moving the cursor.