By using ubiquitous office badge clips with attached strips, I created an easy to apply hanging mechanism that goes on, and comes off, easy as pie.
This works great if you have gutters. You may find a way to get it to work without them, but I guess it would depend on your roof.
Step 1: Get some office badge clips
I hung 5 strings of lights, with 25 lights each, with 30 badge clips. That's 6 clips per string of lights. These are the strings with the large bulbs. Strings with the small bulbs could probably use fewer clips. I also used a few extra badge clips here and there as I went around corners or encountered other obstacles, so get a few extra.