How to transfer files from one iMac 2008 to a iMac 2015

In what context?

How many?

Regularly or just once?

You can do everything from setting up a small network over LAN to just dragging them to a flash drive and then off again. If you are doing this as part of setting up a new computer there's special ways to do that. So we really need more context.

If you're upgrading from an iMac 2008 to an iMac 2015 and wish to migrate your documents and files and related contents, click on the following blue-text link > Move your content to a new Mac - Apple Support