If you have a driver's license, voter registration or any sort of state ID, you're typically in your state's pool of potential jurors. If you're picked to serve on a jury, it's a paying gig, but it often pays much less than you earn at your day job. As if that's not bad enough, you have to pay income tax on the money.
You'll never get rich serving on juries. As of 2012, jury pay at the federal level and in many states is $40 a day; in Arizona, you earn $12 for each day you spend in court. Some court systems offer better rates for long trials that could impose real financial hardship. The federal rate rises to $50 a day after 10 days of service. Arizona's Lengthy Trial Fund pays up to $300 a day for lost income, provided you can document your loss.
Unless you live in walking distance of the courthouse, it's standard practice to pay you a per-mile reimbursement for the costs of driving to the courthouse, along with any fees for parking there. If you have to stay overnight because the trial lasts more than a day or you're far from home, the court may provide some sort of stipend to defray costs. Minnesota reimburses jurors up to $50 a day for child care.
Report your jury pay on your 1040 in the Income section on the front of the form. The IRS says to write it on line 21 for "other income." Travel reimbursement and child care are money that you receive to cover the costs you incur, so you don't have to report those as income. If you earn more than $600 in one year serving as a juror, the court will send you a 1099 stating the income. When it's any lesser amount, it's up to you to track how much you earned.
Given how little you earn as a juror, your employer may defray the costs by paying you your regular salary while you're sitting in the jury box. In return, your boss may require you turn over your juror pay to her. When that happens, you still report your jury pay, but then you subtract it back out of your income. To do this, use line 36 of your 1040, where you total up adjustments to your gross income, to record how much jury pay you gave up.