Hi Flybot,
I've just completed Stage 1 last night, The Spatial Reasoning Aptitude was easier than I thought, although it may be due to the fact that I had already gone through similar tests when I first apply for the Navy.
Find the odd one out as you said, stay focused and you should be just fine.
As for the Diagrammatic Reasoning one it was pretty easy at the start and was able to progress through it without the need of scrap paper but around the 6th round it eventually got harder so I'm not sure how well I did. (I should have used paper and pencil but did everything mentally
).
INPUT, PROCESS, OUTPUT, you wil have to either guess which process was used from the INPUT to the OUTPUT, what was the original INPUT to get the OUTPUT through to the process and so on...
In the latest "rounds" there may be more than 2 processes involved.
Take notes
Wish you the best luck!