Verbalise everything.
Your instructor will tell you this but it is very important. Before you do anything, like turning, changing the throttle, pitch, mixture, anything at all, say what you are doing and why you are doing it.
It is a good habit to get into because the flight examiner is going to want to hear it.
Here are a couple of examples:
1) In my type, after takeoff we climb at 80 knots to say 500ft then enter a cruise climb at 90 knots. The reason we do this is that 80 knots is the best rate of climb and gets us to a safe altitude as quickly as possible. We then lower the nose and continue the climb at 90 knots because with a lower nose attitude, we have better forward visibility and the increased speed means better engine cooling.
Before lowering the nose, I was taught to say 'I am now going to lower the nose to climb at 90 knots which gives us better forward visibility and increased engine cooling'.
Then you lower the nose.
2) Forced landing without power.
If you are on the downwind leg of the forced landing without power but you're too close to the field, you will want to turn away from the field slightly to improve the spacing. Tell the instructor or examiner that is what you are doing. "I am turning away from the field to achieve correct spacing."
You'd think it would be pretty obvious why you are doing these things like increased spacing or lowering the nose but you want them to know that you know what you are doing.
Verbalise ALL lookouts "clear left, clear ahead, clear right".
Coming into land: "I am a little bit high so what I am going to do is [bla bla bla]" and then do it.
Basically the key is to talk talk talk. As you said, your next hurdle is the CPL and the examiner wants to hear you rationalise every single thing you do.
Learn the flight manual for the type you will likely sit the test in. Know it back-to-front. Your flying school will likely have a copy you can study.
Learn the rules and regulations; they will ask some pretty obscure things in the test.
Learn the climate for your area. The examiner might ask you about what the effects of certain things like cold fronts have on the area and how the terrain has an impact on it.