There are some disks you should have on hand for your Apple II and I have provided links to their disk images under Links and Disk Images.
Diversi-Copy. You should have a copy of this program for copying regular diskettes. It’s fast and very easy to use. It copies disks and formats data disks for ProDos, Dos 3.3, Pascal and CP/M.
If you are going to work with ProDos, you should have a System User’s Disk and I use the ProDos 8, v4.02 System Disk.
For DOS 3.3 there is DOS 3.3 System Master From January 1, 1983.
Apple supplied a set of disks to help you get to know your Apple II better. You can choose the ones for your specific model IIe, //c or //c+ at Asimov under images, masters, model specific.
If you have any copy protected software, and the Apple II had tons, you’ll want Copy II plus or Locksmith. There are several versions of Copy II plus available from Asimov at the link for Copy II plus. Version 8.4 appears to be the latest stable version. People have reported problems with the 9.1 version.
—
Last Update: 05-Aug-13 at 6:23PM
For Copy II+, I see that a recent comp.sys.apple2 thread discusses how the recommended stable build is 8.4 and 9.1 should be avoided.
https://groups.google.com/forum/#!topic/comp.sys.apple2/CiTKYiKtX2M
Thanks, I updated this page to reflect this.