Basic

C-a C [F2]
Create new tab
C-a A [F8]
Rename current tab
C-a C-a [F3]
Go back to previous tab
C-a <0-9>
Switch to tab #
C-a "
List of current tabs
C-a d [F6]
Detach

Splits

C-a S [S-F2]
Split horizontally
C-a | [C-F2]
Split vertically
C-a TAB [S-F3-F4] or [S-Cursor]
Jump to next region
C-a X
Remove current region
C-a Q
Remove all but current region
C-a :resize [C-Cursor]
Enter # columns/lines in split