Here is an incredibly useful set of prompt questions for Guided Reading, some of which are based on the QCA analysis of reading.
The questions will enable you to pick out a particular Assessment Focus and ask questions directly relating to it.
I have printed my set onto coloured paper - a different focus for each AF. I have laminated them, cut them into strips and made a flip book out of them.
The formatting might not be quite right for some computers and I apologise if this is the case, but it is a Word document so you will easily be able to amend it to suit yourself.