Like this one at Cheaper Than Dirt's blog, the "Babineaux Method" for reholstering Glocks:
To ensure safe holstering, today’s professionals are beginning to utilize a method that has become known as the Babineaux Method.As they say on Wikipedia: 
While the idea seems sound at first, keeping the trigger from moving rearward, the method is seriously flawed because it involves sticking your finger inside the trigger guard while holstering. Bad Idea.
If you are at all hurried, or shaky, or not paying attention, your finger is now only a half inch away from becoming exactly the trigger-jostling foreign object you're trying to guard against.
The column gets double extra bonus fail points for showcasing a photo of a guy stuffing a Glock into a floppy $10 Uncle Mike's neoprene clip-on holster pointed right at his junk in the suddenly trendy appendix-carry position. You could possibly come up with a better setup for disaster, but it'd take some work.