Have a firm rest for the camera and if possible, use a tripod. But if you wish to take an instant photography, set the camera against some solid object and moving only the finger to activate the shutter release.
Choose morning or evening time since there is much more drama in the light of the low-sun of morning and evening.
Pay some attention to composition with some foreground elements like tree branches, monuments; upper portions of interesting buildings can be handy as frames for a cloudscape.
If you wish to include the halo or corona around the sun along with the clouds find some object in the foreground to block out the solar disc.
Since clouds are ephemeral so click and catch the moment, keep the camera ready by reducing the shutter speed by a few stops in automatic camera to get better textured and well defined look of the clouds.