Mention the fact that you're a senior citizen when you make your travel reservations. In most cities, people over the age of 60 qualify for reduced admission to theaters, museums, and other attractions, as well as discounted fares on public transportation.
At any rail station in France, seniors (60 and older, with proof of age) can get A La Carte Senior, available online at www.senior-sncf.com. The pass costs 53€ ($69) and is good for a 50% discount on unlimited rail travel throughout the year. The carte also offers reduced prices on some regional bus lines and half-price admission at state-owned museums. There are some restrictions -- for example, you can't use it between 3pm Sunday and noon Monday or from noon Friday to noon Saturday. There's no discount on the Paris network of commuter trains.
Members of AARP (formerly known as the American Association of Retired Persons), 601 E. St. NW, Washington, DC 20049 (tel. 888/687-2277; www.aarp.org), get discounts on hotels, airfares, and car rentals. AARP offers members a wide range of benefits, including AARP: The Magazine and a monthly newsletter. Anyone over age 50 can join.
Many reliable agencies and organizations target the 50-plus market. Elderhostel (tel. 800/454-5768; www.elderhostel.org) arranges study programs for those ages 55 and older.
Recommended publications offering travel resources and discounts for seniors include the quarterly magazine Travel 50 & Beyond (www.travel50andbeyond.com); Travel Unlimited: Uncommon Adventures for the Mature Traveler (Avalon); 101 Tips for Mature Travelers, available from Grand Circle Travel (tel. 800/959-0405; www.gct.com); The 50+ Traveler's Guidebook (St. Martin's Press); and Unbelievably Good Deals and Great Adventures that You Absolutely Can't Get Unless You're Over 50 (McGraw-Hill), by Joann Rattner Heilman.