Below are just a few simple tips and tricks I've come across, relating to the Commodore 64 and 128.
The quick way to load a disk
Switch between 80 column and 40 column mode on-the-fly
Saving over an existing file on floppy disk
View a file-specific disk directory
A command line reset button
Stop the disk chatter - Originally published in Loadstar, issue #8
Load and Run a BASIC program with one keystroke - Originally published in Loadstar, issue #10