It's a good idea to get hold of some past papers for 11+.
A couple or more years ago there was a programme on TV about grammar schools and what was required for entry; it showed many families who paid for tuition, at great expense. Some of the kids felt pressurised because their parents gave up so much to help them. Very few passed the exam.
I have to say the primary school teachers were not impressive.
I decided I'd have a go at doing the 11+ again, just as an experiment. I found papers on the internet and timed myself. Not exactly 'exam conditions' but I was on my own, it was quiet (and I didn't cheat). It was difficult to think myself back in to a 10 year old's head, style of writing, vocabulary and experiences are so different when you are a child, but I tried.
The hardest bit was the non verbal reasoning. I ran out of time there so didn't quite complete that section but managed to scrape through it. The rest of it was fine, I enjoyed doing it.
Hee hee, it probably sounds like a silly thing to have done but the TV programme was so interesting and really drew me in. If I'd still had a child of the age to be preparing for the exam it would have been extremely useful so I definitely recommend it. It's good to know what they are up against and the areas in which they need practice.
Interviews practice is also important.