How to create an ISO image?

So, I'm clueless. I just want to be able to create an iso file and burn it. The burning part should be no issue I'll just use the Disk Utility for that. But How do I make an iso with multiple files? Thanks

If you have a bunch of files you want to burn to a CD/DVD, then there's no need to make an ISO first. OS X has the ability built in to burn then straight to the disc.
How to Create a Burn Folder in Mac OS X Lion - For Dummies

If you need a more advanced tool, Burn is a pretty popular freebie.
Download Burn for Mac - Easily burn data, audio, video disks and more. MacUpdate.com

You can also use Disk Utility to create a disc image, although I'm never sure if that's the same as an ISO.