In the multiple choice bit, I looked at the clip carefully, and kept in mind that giving things away is largely unacceptable.
For example, don't just hand out money to anyone who complains, unless they prove they are owed it.
Also, watch for potential hazards, as the options to help immediately might be hazardous or otherwise cause difficulties to other customers, such as where you might be leaving trolleys, boxes or other large objects if you help the customer immediately.
In the spot-the-problem bit, it can be really obvious, such as large messes or the labels being completely wrong, right down to where things are, or perhaps aren't, on the shelf.
The maths bit seems pretty simple, you shouldn't have any problems with that bit except perhaps the last two or three questions which might be a little difficult to work out in your head. Use the scrap paper provided or the little blank patch in the box to jot out notes if you need.
Finally, the personal opinions bit is also pretty simple, just follow what it says. Some questions, such as the stealing ones or the "I am lazy" ones, are pretty simple to choose the option, but if you are an independant worker or you like to have directions given to you, make sure you answer those ones truthfully. If they hire you thinking you are good with initiative and know what you are doing, then find out you aren't, they probably won't keep you through after the probationary period.
*end of text wall*
EDIT: Oh, and if they do what they did for me and then talk to you about transport, past experience, school etc., emphasize past experience (I've used tills in a garden centre on Work Exp. before) that is relevant to daily tasks at the store, and say that transport is not an issue at all. You can go home, research the transport options, and find it out later. Giving them concerns about taking on someone who may intermittantly not turn up will really cripple your chances of success.