Hey Aurelie -
Here is a link to a template: http://www.its.swin.edu.au/projects/templates/UATChecklistTemplatev1.1-[ProjectName]-[ver]-[YYYYMMDD].docx
To frame this, UAT is about ensuring that the users requirements are met. It is not systems testing to make sure data/processes are kicking off correctly, but rather it is geared around the users making sure their requirements are being met... So, in general, I would apply this list of defined requirements and then walk through with the user whether or not the requirements were met and the expected result is achieved.
Hope this helps!
