Maybe one day I'll even apply to be in the audience. You can sign-up online.
But there's no official guidance on how to ask a question or make a comment from the studio floor. As always, I'm here to help:
1. Affect mock outrage over the issue under discussion, preferably in a way that suggests you have lost all sense of proportion.
Tip: use the formulation (how dare/can [panellist] say/claim [opinion expressed]) + (when [large number] of [interest group] are [emotion/sufferance]).
Example: "How dare the minister claim that not every senior citizen needs a free bus pass while hundreds of thousands of pensioners are still angrily awaiting a hip replacement?"
2. Make an ideological non-sequitur.
Tip: if you're Pretend Left, then feel free to use "neo-con" and "neo-liberal" interchangeably (don't worry about the distinction) to describe anything that suggests a market solution; if you're right-leaning, then "Soviet" is a good catch-all for anything that might require the State taking an interest.
Example: "And if the government was really serious about helping people reduce roadworks in their communities then it shouldn't have imposed Soviet style targets on local councils, should it?"
3. Throw in a dubious personal anecdote.
Tip: make sure that the subjects are just far enough removed from you for you to plausibly deny any further knowledge if questioned.
Example: "My son's girlfriend was made redundant [while her boss was paid a massive bonus] / [when the Health & Safety shut down her office].
4. Confuse the rest of the audience.
Tip: put a left-wing thing at the start of the comment, then make a sharp right and throw in something out of that morning's Daily Mail letters page. Employ the other three techniques above, and you have what I like to think of as the Question Time Money Shot.
Example: "How can an MP that wants to take us back to the days of Thatcherism just sit there and criticise the millions, like the parents of the kids I teach, who rely on benefits to avoid starvation and who want to work but can't...because all the jobs have been taken by immigrants?"
If all goes well, it should inspire one of those weird half-cheer/half-boo rumbles that sounds like everyone simultaneously throwing up in their mouth a little bit.