Getting people to come up isn't a problem, there is always someone willing and I offer a line I use at the start of my shows (I have worked in the roughest bars with all kinds of cretins and this prevents lots of problems).
'I would just like to say a couple of things before we proceed with tonight's show; firstly if you are lucky enough to be one of the participants on tonight's show I will not embarrass or make a fool out of you in anyway shape or form and secondly if I ask you a question please answer to the best of your ability, do not answer with YOUR THE MIND READER as I have heard it a thousand times and it is no longer comical'.
Using the above line prevents anyone thinking you are going to ridicule them and secondly prevents the one c0ck using the ever favourite line a cretin use 2 birds one stone.
If you do get a participant that is an ar*ehole, don't use him find out if they are first ask a couple of questions if they answer in a sh*tty tone or like they cannot be bothered being there, just say I might come back to you later (don't be afraid to send them back to their seat). Or if you have something sure fire use that and the more he tries to be an ar*e you know its going to work so he ends up making a plonker of himself.
The material you use is up to you, don't let anyone sway you, its your show and your the only person that is going to know what you are comfortable performing. If you are sh*t you are sh*t, I perform almost every week twice a week and if I said every show went perfectly it would be a lie but your job as a performer is never to let the audience know that it it isn't going perfect. If something happens an unexpected curveball have an out for it, always make the best of a bad situation (at the end of the day there is nothing cooler than predicting an unexpected curve ball
Make sure your show flows, one thing should lead into another there shouldn't be a buckle I wouldn't make my show about doing an effect and then an effect and then an effect because its boring. There should be interesting stories, funny moments and even though silence is golden in the right parts, you don't want massive lapses for the audience to get bored.
Forget about the subjects, think about the presentation and scripting and you are on to a winner and last of all good luck!