Method to observe more

So I have my driving test tomorrow. I'm a really confident driver, and my instructor said I'm already ready after 20 hours of lessons, which is great! However, sometimes I just forget observing around me while doing maneuvers such as parallel Parking, reverse around a corner, and Turn in the road. Is there a good tip to make me remember to observe? Anything that just makes my brain click, while my focus is on not hitting the kerb or something else.

- Thank you, and wish me luck! :)

Note: I do observe, but after observing for couple of seconds, I forget to observe again.

Kind Regards

Kennen