Since I use GTD principles I have a 'next action' list to work from. Nevertheless I sometimes need to go back to the original email or hardcopy to look at the details of what needs to be done. I found it sometimes difficult to make some kind of link between my list(s) and the origninal documents.
I realy liked the 'tracking number' approach described on http://www.robsprotips.com/
What do you think? Any other suggestions?