I presume you are referring to 5.25 inch floppy disks? Isopropyl alcohol is fine to clean the heads with a cotton swab (q-tip).

There are some tutorials online on how to clean a 5.25 inch drive's heads but, you basically just remove the top cover and then gently lift the head assembly and clean it with a cotton swab - here's one video: https://youtu.be/kCBLJMqTFng.

However, chances are that, after 30 years, your floppy disks would have picked up some oxidation which would make them also unreadable. There are ways to try and clean those as well - one method that I've tried is to clean the disk surface with a cotton swab that has been absorbed in purified water. You then clean both sides of the disk and rotate the disk until you've cleaned the entire surface. Very time consuming and you have to let the disks dry out.

Actually I have some software on both 3.5" and 5.25". But most of the items are on 3.5".

What about cleaning a 3.5" drive?

If I don't clean the 3.5" disks ahead of time, and try and clean them after a failed read, that shouldn't hurt anything right? So long as I let them dry before trying again?

There are plenty of tutorials. Here's one: https://youtu.be/m6CEVtOlpoY.

If you try to read an old floppy disk and it is "dirty", then you just end up having to clean the floppy drive's heads again.

But, you don't have to clean the floppy disks - it's just a suggestion should you suspect them being very "dirty".

You have to be careful not to knock the drive heads out of alignment. Apparently you can only correct this with some complex juju involving exotic proprietary software and an oscilloscope.

Errius wrote:

You have to be careful not to knock the drive heads out of alignment. Apparently you can only correct this with some complex juju involving exotic proprietary software and an oscilloscope.

I have prematurely greyed many hairs attempting to align floppy drive heads.