I don't think you can do a whole lot to prepare for these beyond getting a good night's rest beforehand if possible.
Couldn't disagree more.
The prep is part of the assessment. Unless you're a very clever individual that's naturally gifted at verbal reasoning and computer games with backwards flight directors (I'm certainly not), I would strongly advise putting the leg work in.
With a bit of research and some minor financial investment in some prep software / books (SkyTest and Assessment-day spring to mind) these tests are entirely passable. The capacity test at the end of the first stage is something that can't really be rehearsed but in reality it's only as stressful as dealing with a lengthy non normal in the descent. If you do well in 3 out of 4 then you're probably in with a good chance. (bearing in mind it's an overall score across the 4 different tests on the day)
BA aren't after geniuses or **** hot pilots (if they were I'd still be back flying in LoCo land), just people that will fit in and are prepared to work hard, learn and progress. If you don't want BA enough to do so then you're probably best saving your days off for something more constructive and let someone else have a go.
As for a good nights sleep the night before, absolutely, but cannot be guaranteed. I had an awful nights sleep before 2 out of 3 stages. The hard work prior to attending each stage got me through.
Just my two cents worth.
Evening All
2W2R