So, many of you are probably familiar with this technique, but if you're not, then here's how to do it.
1. Get whatever you want to be on the rope, such as the minifigure in this creation.
2. Find a way of attaching your chosen item(s) to the rope. For example, I found that the rope jams in between the overlap of the legs nicely.
3. Get your whole scene set up, but don't attach whatever you are trying to attach to the rope yet. It's easier this way. Also, make sure that your rope is nice and tight, so that it doesn't do what mine is doing in the photo and appear to curve upwards slightly.
4. Now hang the whole scene upside down. I built a little Lego frame to do this.
5. Attach your item(s).
6. Take photos!
7. Above all, have fun and experiment. There are definitely more uses for hanging thigs upside down than a little tightrope walker. There was someone a while ago who posted a few little builds much better than this one using this technique, but I can't remember who it was. If anyone knows, then post a link in the comments.
Notes: I've been wanting to try out this technique for a while, so here it is.