Europe in 11 days? Need advice

[linz7777]

Europe in 11 days - need help!!!
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Hello. I'm coming to Europe in October and looking for any good advice. I will be flying into London.. .. . and then would like to see Paris and at least one other country while I'm there. Everyone keeps telling me to try not to see too many places at once, but considering I've never been there - of course I want to take in as much as possible.

Questions:
1.What is the best form of transportation? Thought about purchasing a rail ticket, but is there a better way around?

2. Recommended "must sees" in Paris and London? Where would be another good destination considering my time restraints?

3. Should I reserve hotel stays before I arrive or find places once I arrive according to where I go?

Any advice/recommendations would be greatly appreciated! I'm traveling with my brother and we're in our 20's - first time to Europe for both of us! Thank you!!!!