When held at certain angles, your camera's lens might move slightly due to gravity. To prevent that "zoom creep" from happening, put one of those inexpensive rubber bracelets around your lens.
This has a second benefit, Sarah Hipwell says on Digital Photography School: you can secure a Ziploc bag around the lens to protect it in the rain.
Check out a few other camera hacks at the link below.
5 DIY Hacks to Have in Your Camera Bag [DIY Photography School]