Its worth working out what orientation you want the lens to be at before you mount it.

Personally, I prefer my main controls to be be mounted at the top of the lens - while others prefer them mounted to one side.

Its a personal choice - no right or wrong way - just what ever works for you.

If you have never thought about it - just check your other lenses - its easier to operate them blind (by feel) from beneath the darkcloth if they all share the same basic positioning of the controls.