Start with the Bond Books called How to Do.... (such as How To Do Verbal Reasoning papers) as these will provide you with the techniques required to do all the different types of question quickly and efficiently.
I am very sorry to have to disagree with you, nethermancer, but the Redbridge tests are set by GL assessment, and Bond VR materials are not appropriate practice.
baadil, there is more information about the Redbridge tests here http://www.elevenplusexams.co.uk/school ... ge-11-plus
and a link to appropriate practice materials, all of which are available from our bookshop, mostly at discounted prices compared to high street retailers. There are versions of many of the materials for younger children.
For Redbridge VR, all Patricia's tips for DIY preparation for Bucks are equally applicable to Redbridge viewtopic.php?f=3&t=30178
I can't be of much help on NVR, but I am sure that others will suggest tips for preparation.
Apart from using published materials, encourage a wider vocabulary and rock solid times tables. There is advice on preparing younger children for the test here http://www.elevenplusexams.co.uk/prepar ... -3-year-4/
and if you explore the wider website that surrounds this forum, you will find a lot of helpful information.