removing duplicate jpeg files

[olddognewtrick2]

I've been trying to free some space by putting my picture files onto a memory stick.

I don't seem to be able to just cut and paste the files.

I need to copy them onto the memory stick, but then when I try to delete the copied files it also seems to delete the files on the memory stick.

When I try to recover the files from Trash, I get duplicate files.

I have LOTS of pictures and don't look forward to manually going through and deleting all of the duplicates.

So my questions are:

How do I move the pictures onto the memory stick cleanly

and

How do I delete duplicate files?