Most major U.S. tech companies have offices here, and Web startups like Last.fm and Moo are thriving.
How to get around: The Tube is the fastest and cheapest way to go. Buy an Oyster, a prepaid card smart enough to give you discounted fares for one-way trips and charge you the lowest possible rate for all the journeys you make during the day.
Where to find free Wi-Fi: Leicester Square, the pedestrian center in the West End of London, is blanketed in wireless signals.
Where to get a trim: Headmasters is a U.K. chain offering quality haircuts for between $60 and $150, with a complimentary head massage and refreshments.
Best place to get down to business: Head to the Wolseley for a power breakfast meeting (160 Piccadilly; 44-20-7499-6996). A hearty English breakfast is $27.
Best place to celebrate closing the deal: Professionals flock to Club Gascon (57 W. Smithfield; 44-20-7796-0600), where the kitchen whips up delicious, tapas-style portions of foie gras and other delicacies from southwest France.
What you might not know: Business cards tend to be an afterthought here. Don't be surprised if your counterpart fumbles to find one or can't find it at all.