I've finally found a method that works very often for me. Here's how I do it:
I've been using the ladder in "The Prisoner". It's the one that appears after you kill the beholder, that leads up to the Memnos Blossom.
1. Get on the ladder, then back off of it. This will line you up, so you're facing directly at it.
2. strafe to the right a tad (See image below). Line you're self up, something to that effect, with the right edge.
3. jump into the right edge of the ladder, always holding forward. If you're lined up right, you'll notice that your toon will jerk against it a bit, and then grab on.
4. Still always holding forward, if it was done right, you should start to loop at the bottom.

This method is kinda random at success, But has been a lot more successful than the whole "Land at the bottom of any ladder" Method.
I've found that coming in contact with the edge
before you reach the peak of your jump works best for me.

Good luck!

EDIT: Oddly, I've only been able to get this to work so easily with the ladders in The Prisoner...