Welcome to GFE,
princessjazzle.
Not sure what advice you're looking for - but based on your post I can advice the following:
London – 4 daysGood start of time to adjust - not sure where you're flying from, but jet lag may be a factor for the first day so don't plan on cramming too much in to that day. With 4 full days you may find that you either only have time to see just London, or if you've been there before you could fit
one(and only one) day trip in to somewhere close (Stonehenge, Bath, Windsor, Oxford) if you're so inclined.
Paris – 4 days Book as far ahead as you can (90days out is usually when they release seats for booking) to take the Eurostar train from London to Paris. Quickest way and better than mucking about with flights on this route. 4 full days will allow again for exploring plus a half-day to Versailles.
Amsterdam – 3 daysThe Thalys (fast) train on this route is the best way to travel. 3 full days is plenty to explore the city, no day trips.
Berlin – 3 daysFlights with Transavia between AMS and Berlin are usually fairly cheap, otherwise there is an overnight train which stops in Cologne briefly if you want to jump out, take a quick look at the cathedral, then jump back on.
3 full days in Berlin will be enough to explore just the city, no day trips.
Prague – 2 daysTrain Berlin to Prague is the best method, and You may find you want 1 more full day here as there is a lot to see and do. A lunch stop for a few hours between the two cities could be Dresden if you're interested.
Venice – 3 days2 full days usually does most people for time in Venice, but 3 will allow a day trip out to the islands like Burano or Murano or even Torcello.
Trains - in Italy there are many trains per hour between the destinations you've listed, so you can look on
www.trenitalia.com for an idea of times.
Florence – 2 daysNot sure what your interests are here, but I would be inclined to add 1 more full day if you plan to see a lot. Otherwise 2 full days will be enough for the city only.
Rome – 3 days3 full days will let you scratch the surface of Rome, but don't plan any day trips.
Barcelona – 4 daysfly Rome to Barcelona - look at Vueling or Iberia for flights.
4 days in Barcelona are enough to get a good amount of time to explore the city.
A few questions/notes:When you write "days", do you mean full days? That is, 3 days = 4 nights? I've taken it to mean this in my notes above, but if you don't mean this then that will alter some suggestions.
What are your interests in each city - museums, food, etc? If you are looking at museum visits, be aware that Mondays (and in Paris Tuesdays as well) are the closed day for most museums, so plan your visits accordingly.
I've listed a combination of trains and flights for each sector, and from the looks of it you won't need a rail pass, esp in Italy as train travel is cheap enough.
Backpacking - if you are planning on staying in Hostels then start booking pretty soon as the good/cheaper ones get booked out quickly.
Flights to/from Europe - if you haven't already, look at an open-jaw ticket which will let you fly into your start city and out of your end city, saving time and the need to back track to the start city just to fly out.
That should get you going on the next stage of planning - good luck!
