Running a virus scan before launching any of the programs on the disk will prevent infection. Don't share floppies. Even a well-meaning friend may unknowingly pass along a virus, Trojan horse, or worm. If a friend passes you a foreign floppy, suggest an alternative method of file sharing. Don't boot from a floppy disk.
Floppies are one of the most common ways viruses are transmitted.
If you are using a floppy while working on your computer, remove it when you shut the machine off or the computer will automatically try to boot from the floppy, perhaps launching any viruses on the disk. Don't download programs from the Web. Unreliable sources such as Internet newsgroups or Web sites that you haven't heard of may be willing providers of viruses for your computer. Avoid downloading files you can't be sure are safe. If you do have to download from the Internet, be sure to scan each program before running it.