TD's Handy Hint of the Day for newbie tripod users...
You are out landscape snapping, the wee plate (the QRP or quick release plate) of the tripod is screwed firmly to the bottom of the camera and secured in it's bed on the tripod by the locking lever. Great.
You are snapping in landscape orientation using the wee spirit level to keep that horizon square.
You decide that you want to take an image in portrait orientation.
Now, to do that you must rotate the camera ninety degrees and of course you do that by using the tilt lever on the tripod....................
I see so many people tilting the camera anti-clockwise to do that, so that the camera is now hanging to the left hand side of the tripod, which keeps the shutter release button and the exposure controls nice and handy and the top edge of the camera..............................but, that also means that the weight of the camera/lens combo is acting on the screw holding the camera to the tripod in a manner which would/may allow the weight of the camera to unscrew itself and droop, possibly even fall off.
So, for portrait orientation, tilt the camera clockwise..........the controls/shutter button are now in a slightly awkard position at the bottom of the camera......but the weight is now acting against the thread on the screw and if the camera rotates at all it will serve to tighten and not loosen the screw.
A little awkward but much more secure.