Prague's hostels not only are some of the cheapest places to stay but also are great for meeting other travelers. You don't have to be a card-carrying member of the International Youth Hostel Federation (IYHF) to lodge at most of them.
If you want to make some music or do some magic busking for money, you can do so legally anywhere in the city. If you want to sell something, though, beware that authorities require permits for those who wish to hawk on Charles Bridge and elsewhere.
If you're planning to travel outside the U.S., you'd be wise to arm yourself with an International Student Identity Card (ISIC), which offers substantial savings on rail passes, plane tickets, and entrance fees. It also provides you with basic health and life insurance and a 24-hour help line. The card is available for $22 from STA Travel (tel. 800/781-4040 in North America; www.sta.com or www.statravel.com), the biggest student travel agency in the world. If you're no longer a student but are still under 26, you can get an International Youth Travel Card (IYTC) for the same price from the same people, which entitles you to some discounts (but not on museum admissions). Travel CUTS (tel. 800/667-2887 or 416/614-2887; www.travelcuts.com) offers similar services for both Canadians and U.S. residents. Irish students may prefer to turn to USIT (tel. 01/602-1600; www.usitnow.ie), an Ireland-based specialist in student, youth, and independent travel.