Serial Line Transfers:
The most common method of transferring disk images is through a serial line. To do this, you must connect your Apple to your PC with a serial line and null modem, then run one program on the Apple which reads data off the disk and sends it out over the serial line, and another program on the PC which collects data from the serial line and saves it to a disk image file. This system can be difficult to set up initially, but once it is working it is very fast and convenient.
There are a number of files on ftp://public.asimov.net/pub/apple_II/ which contain programs and tips to help you transfer disks in this manner. One noteworthy program is Apple Disk Transfer (adt120.zip), which can simplify the setup process by automatically installing itself on your Apple through a serial line.
Modem Transfers:
If you have a modem and terminal program on both your Apple and PC, you can take advantage of that to transfer disks with very little initial setup. Here's what you do:
Transferring Through 3.5" Disks:
One final way to transfer disk images is to copy the data onto a 3.5" disk, and then use a Macintosh to transfer the data from the 3.5" disk into a PC readable format. The advantage of this method is that it does not require a serial card or modem. However, it does involve a number of steps: