With yesterday's verbal test at Tiffin boys, my son has just completed this year's 11+ exams. To give you a flavour of things from our experience:
I tutored (coached) my son. We started the process only towards the end of August 05. In our case he is reasonably ok in studies. He enjoys problem solving, number and word puzzles, etc. This statistics was important in our case and based on that I was able to assess his potential and make the appropriate starting point and hence didn't start a year early!
Tiffin follows Nfer formatted verbal and non-verbal tests. In my view this is good because many children don't fancy doing english test that includes essay writing.. More over the Tiffin uses multiple choice question format which again in my view is an advantage.
In non-verbal there are mainly 5 types of questions. 11+ practice paper publications also have books that are full of 'tips' and 'tricks' to enable the children to grasp the different logics to look for as well as patterns. These are good and with practice children will be able to easily apply different logics to each question and identify the correct one. Don't just limit with the practice papers. Browse the local library and use any books you find on this subject.
For verbal reasoning vocabulary plays an important role. Possible Nfer word list can be downlaoded from this site (posted by Mike Edwards). Tips and Tricks kind of books available to purchase and there is a freely downloadable document available from Athey website as well.
Have a plan. I used to keep a register of all the questions (purchased, free downloads, etc), answer sheets and answers with unique number scheme (VR-001, VR-002, etc.). Plot the score, time taken and date for each trial. You can record more/less info depending on your interest. Start with simple examples and not with the actual papers. Identify the practice papers according to their level (easy to hard) and introduce then accordingly. Once the child attains a level with the full understanding of different logics, patterns, types of questions he/she will be ready to handle any practice paper.
I stop here. Otherwise I will be here all day writing a book! Please post for info on these subjects and there are many willing parents and tutors to help.