Some things I've learned

1. The Heathrow Express is best way to get into London, unless you are 3+ people with luggage, in which case a black cab is cheaper.  Don’t ever take the Piccadilly Line (Underground), it may be cheaper but it takes forever and you’ll arrive at your hotel feeling like a loser after an hour surrounded by all those sweaty backpacker
2. There are a few good hotels around Paddington, which is right at the other end of the Heathrow Express.  These are actually easier to get to and far nicer than the Heathrow airport hotels which cabs hate taking you to, forcing you onto horribly unreliable shuttle services
3. Without shredding your nerves with traffic stress, it is almost impossible to schedule appointments with two ‘London-based’ pharma companies in the one day unless both are in either Cambridge or Uxbridge.  If you're not driving don't even contemplate it
4. British clients assume that you drove to the meeting.  So do Americans.  European clients do not
5. The pharma companies based in Cambridge aren't as near to the rail station as you would think / like
6. Take a cab from Edinburgh airport
7. Meetings in Dublin are rarely anywhere interesting or fun like Temple Bar.  If you want anything like an Irish experience you'll need to get the hotel to order you a cab
8. No one wears a tie in the UK.  Nor does anyone carries a business card
9. Travel everywhere by air conditioned cab in Singapore.   The alternative is to arrive at the meeting sweating like a pig
10. Vodafone doesn't have mobile roaming in Korea.  Annoying
11. Take cabs in Seoul.  The streets are badly marked and Korean is impossibly hard to decipher on the run
12. Don't expect to use your gym gear in Beijing, the notoriously poor air quality is such that you’re in danger of making yourself ill
13. If you want to start a mild yet interesting argument over a meal in Malaysia ask the table for the recipe for an authentic lahksa 
14. An Australian wanting to compliment someone from the Gulf merely needs to say that the Burj al Arab is the architectural equal to the Sydney Opera House.  You won't be lying
15. Do not attempt to diet on a trip to Singapore.  The food is just too good
16. Discussing international travel is a great way to make conversation in Europe.  In the US it only serves to remind them that you're not from under around here 
17. Never discuss politics or religion with American clients.  When in doubt ask people to name their favourite Will Ferrell film
18. Everyone in Europe loves Barcelona FC (except a few bitter, bitter people from Madrid and Manchester)
19. Never wear leather-soled shoes in Scandinavia or Sweden in winter.  You will slip and injure your head, neck, shoulders or back
20. Don't be afraid of the Metro in Paris.  But don't confuse it with the RER.  Don't be afraid of the RER either
21. There isn't a weekend’s worth of fun in Warsaw.  Go to Cracow instead
22. Contrary to their carefully cultivated reputation, Finns have a terrific sense of humour, however, they're prone to annoyance if you actually make them laugh out loud
    
23. Public transport is brilliant in Basel.  The iPhone 'maps' app has all the details
24. Germans do not appreciate self-deprecatory humour.  Never attempt to break the ice at the start of a meeting with a flippant comment at your own expense as it will make you seem inconsequential in your audience’s eyes.  Let them make the first joke
25. The Spanish like shaking your hand every time they see you, as often as ten times over the course of a day-long meeting.  This is nice
26. If someone mentions that Paris, Barcelona, Milan, Luzern or Nuremburg are an option for an upcoming meeting then push hard to make it happen.  These cities are everyone's cliche favourites for a reason
27. Brussels isn't much more fun than Warsaw
28. Don't stress too much about mobile / data roaming charges.  Life’s too short