Each time a lawyer tries to pick people they think will agree with their side in the upcoming case. Both lawyers will approach all potential jurors as if they are long lost friends. This gives you a great chance to escape.
As soon as you see the lawyers for the prosecution and for the defence, pick one, or both, as a potential `enemy'. The stronger you can feel the emotion, the more powerful your body language is. Shake your head, glare, make faces. The lawyers and any staff with them are carefully noting all reactions by all potential jurors. They are trying to pick out any prejudice against them, against their client or even against their case. Showing a prejudice, even if you do not have one, gets you quickly out of the courtroom. Almost all lawyers will excuse any potential juror who they cannot see as a potential friend. Their questions will be delivered with so much fake charm and friendliness as they can master.
The Judge may ask questions of his own. For example, in a case involving car theft, the Judge may ask all potential jurors if they have ever been a victim of that type of crime. Even if you give a positive answer to that type of question, the Judge will only ask if that experience will influence your decision in the case they want you to hear. No matter your answer, the Judge makes his own decision on if you stay or go. Your answer to that second question may, however, cause either the prosecution or the defence to want you excused.
Almost sure to get you off, is a loud "What?!" after any question, from anyone, to anyone. You will be quickly asked if you have a hearing problem. Yell out "What?!", make them repeat the question and then loudly say that you do not have a hearing problem. No lawyer wants to yell throughout the case and a fake hearing problem does wonders to get you out.
Normally, financial concerns will not get you out from Jury Duty. Check with your employer to see if you will continue to get a pay cheque (a surprising number of companies do pay you while on Jury Duty). If not, this knowledge will aid your skill in acting the part of a juror neither side wants.
Health matters are more of a concern. If you are receiving any type of medical treatment, or if you will in the near future, a Doctor's letter will allow you to escape. Many have claimed non-existent health problems, often on the original letter form asking them to report for Jury Duty. As a firm rule, the Judicial system does not check on any claim of health concerns. Most Doctor's will supply a letter to excuse their patient, because of `stress', `headache' or even `inability to concentrate'. However a loud "What?!" to your Doctor will only result in an unnecessary hearing test.