Getting ahead when visiting London

What: Fast train (15 minutes) between Heathrow Airport and London's Paddington Station.

When you get there: Buy ticket from an airport kiosk ($25) or on the train ($25 plus $7.50 surcharge).

In advance: One day before my trip, I bought a one-way ticket with a credit card at www.heathrowexpress.com. It was $25, same price as the kiosk. I printed the ticket at home, a single sheet of paper with a UPC code on it.

Result: At Heathrow, I bypassed long lines at ticket kiosks and hopped aboard the train. The conductor accepted my home-printed ticket without a problem.

Worth it? Yes. And if your flight or trip is delayed, a ticket bought online is good for six months.

What: Long-distance train from London's King's Cross Station to Edinburgh on the East Coast Line.

When you get there: You can buy train tickets when you get to London. However, since British rail was privatized, each company has its own trains, schedules and prices -- and like airlines, cheap advance tickets.

Result: I'd heard that U.S. credit cards did not always work at train kiosks in Britain, so I stopped by Kings Cross a day early to make sure. No problem -- tickets printed. If they don't, a human at the ticket counter also can give you the tickets. At the station, I also checked how much the ticket would have cost if I had bought it that day. It was $209.

Worth it? Definitely. I saved $152.

What: London's top tourist attraction, a giant revolving wheel with fantastic views.

When you get there: At the ticket office next to the ride, it's $28 standard or $43 fast-track ticket with a shorter line.

In advance: The last time I was in London, I booked a fast-track ticket one day ahead at www.londoneye.com -- and it helped me avoid a long line. This time, I booked a fast-track ticket through Expedia ($34) two months ahead and got a voucher.

Worth it? No. But it might be worth it in midsummer, when crowds are heavier.

What: The royal residence is open for tours only in August and September.

When you get there: The Buckingham Palace ticket office could be sold out.

In advance: Buy from www. royalcollection.org.uk ($26), which will mail you tickets if it's at least two weeks ahead or hold them for pickup. I booked a combo Buckingham Palace/high tea ticket through Expedia ($53).

Result: The voucher required me to show up at the Grosvenor Hotel near the palace at 1:30 p.m. on tour day. From there, a guide walked our small group of four to the palace group entrance for a 2 p.m. admission. In 5 minutes, we were through the gates and on the tour. Later, the tea back at the hotel was classic.

What: London's many fantastic West End theaters are a must-do for tourists.

When you get there: Buy at the theater box office in person or by phone.

In advance: If you absolutely can't miss a certain show, buy tickets in advance at www.visitlondon.com. Or try TKTS, the half-price-ticket booth, in Leicester Square the day of the performance.

Result: I went to the TKTS booth and was surprised to see that many shows were nowhere near half-price and the line was slow and long. I walked away. Instead, I chose a well-reviewed show, "Oliver," that was on its final days and showed up at the theater 20 minutes before showtime. Someone had just returned tickets, and I got a $98 main-floor ticket for $58.

Worth it? No. Buying in advance does not guarantee a low price. Buy ahead only if there's a show you can't miss.

When you get there: Many tourists are confused about which pass to get and are intimidated by kiosks.

In advance: A month before my trip, I went to www.visitbritain.com, bought one three-day Travelcard and one preloaded Oystercard, each $35. My plan was to have my husband use the Oystercard and I'd use the Travelcard, and we'd see which was a better value. The cards were supposed to be mailed to me, but when they didn't arrive after three weeks, I e-mailed VisitBritain and was overnighted the cards without charge.

Result: A Tube strike the first day of my trip meant that one of my three days on the Travelcard was of no value. I took 10 separate rides ($3.50) on the Travelcard over the next two days. Compared with the Oystercard ($2.80 per ride), it ended up costing about the same. Both cards were cheaper than buying single tickets ($7 each).

Worth it? No. Wait to buy an Oystercard at a Tube station your first day in London.