Hi China Doll
There are no set rules for providing pub quizzes and the numbers of questions asked may vary from anything between 20 and 100 depending on the amount of time allocated during the evening.
However it is always advisable to vary the level of difficulty so that some answers are easily determined by the majority of quizzers whilst a few answers will probably only be known by a minority.
It is also important to vary the range of subjects included, so as to provide something of interest to all, and I normally include sets of about 5 consecutive questions on one topic followed by another 5 with different subject matter.
There are a number of web sites were you are able to obtain information and the following sites may be particularly useful ....
http://www.quizzyheights.co.uk/