What's the right way to backups photos when using iPhoto?
Your iPhoto Library is contained within a database file on your computer. This file is located here:

/Users/(yourusername)/Pictures/iPhoto Library.photolibrary

That is the file (or technically, package file) that you will want to ensure is backed up to backup your iPhoto pictures.

As mentioned previously in comments, I recommend that you backup your entire hard drive instead of just your pictures. You can use a tool like Time Machine to backup to an external hard drive, or a service like CrashPlan to backup to the cloud.