I have 18 days in Europe. I want to go to London, Paris, Berlin, Prague, Budapest, Barcelona, Rome, Florence, and Venice. I plan to go London --> Paris --> Barcelona --> Rome --> Florence --> Venice --> Budpest --> Prague --> Berlin --> London (Fly home). How shou

If you want to visit a lot of places in a short time, I suggest sleeper trains. That way you can save daytime for seeing the sites, rather than travelling during the day and wasting the night sleeping. As has already been said, though, that is to many places to see in 18 days. You'll just exhaust yourself and won't see much.

Do you have to start and finish in the same place? If not, start with 2 days in Barcelona (one of which you'll probably spend battling jet-lag and accommodating yourself to European climate). Then fly to Rome for a day or two. Take a train to Venice, with a brief stop in Florence - that's a day - and then a sleeper train to Vienna (rather than Budapest). In general, use trains where possible. It's a lovely and cheap way to travel around Europe, and you'll see more than from a plane. Since it's a sleeper train, you'll have a whole day to see Venice, and still be able to get to Vienna in the morning the next day. Another train to Prague - that's just a short hop - and a full day there. We're half-way through your schedule, and it's only been the first week, so you'll probably want to rest a day at that point. I recommend to do it in Berlin. Berlin is a "walk-about" city, big and busy, and you'll want to spend at least two days there to fill up on what's in my opinion the best of modern "European city buzz". All the cities before were beautiful and historic, but Berlin is all that, but also very youthful and hip. I'd advise one more day-stop between Berlin and Paris, otherwise you'll miss out on a huge swathe of Europe. Make it either Cologne or Brussels, both are definitely worth seeing, and easy to get around in a day. You'll need at least two days on Paris, and three days on London, just to get the basics of either. London is the biggest city in Europe by far, three times bigger than any you'd have visited before - a country in its own right, really. So make sure you dedicate the most time for it. Again, use the train - the Eurostar from Paris to London is 2 comfortable hours from city centre to city centre. The above gives us 16 days, so you'll have 2 days extra to add to any stop if you fancy staying longer - or if you want to see Cologne and Brussels on the same trip. Alternatively, you may want to start with a visit to Andalusia (Granada!) before going to Barcelona. And wherever your trip will take you, remember - you'll be wanting to come back to all of those places again, for longer. This is nothing but a taster of the real thing.

Stick to a few regions and maximise your time there. London and Paris are nice and close. Prague and Berlin aren't too far apart either. Rome, Florence and Venice can be done in a week also (although two weeks would be better to take in everything along the way). Pick a few key places, see and enjoy them, then save the places you don't see for your next trip (which you'll start planning as soon as you get on the plane back home!)

I would choose two, or possibly three, of the list and focus on them. All of these cities have many worthwhile sites, well worth at least a week. Your itinerary would be exhausting and only leave, at best, a day to see anything in each city. You will enjoy your trip much more if you pare the list way down and appreciate what each place has to offer

You'll spend more time traveling (waiting and taking trains, airlines and buses) than actually seeing the sights. I agree -- reduce the place you'll be seeing and you'll enjoy your trip so much more.