Year 4 private school assessment/exam - advice please!

[JoTheUnsure]

Our 8y/o ds is due to have an 'assessment' and sit an 'entrance exam' for one space that has become available at a local private school (he's currently in a large state primary school, we put his name on the waiting list for the private school a few years ago).
 
Can you give me any advice on how to prepare for the assessment as we don't have time to get a tutor?
 
He's good at maths and his literacy is okay but he can be lazy/easily distracted. So we will concentrate on improving both of these (and verbal and non-verbal reasoning - I already have the Bonds assessment books).
 
What else should we practice/prepare? Is there an 'etiquette' for the assessment? What kind of non-academic questions will he be asked? Should he attend in his school uniform (if the test is at the weekend)..?
 
Any help gratefully accepted.