What is your budget? Would you rather go by train, or are you perfectly comforable with flying?
There is no standard, one-size-fits-all first time itinerary for Europe. If you want to see the cities you named, they are all highly rewarding. What are your main interests?Are you looking for the picture postcard sights of the great historicl cities? Or would you enjoy a more intimate, more personal and more people-oriented visit to Europe, enjoying markets, small town life, and the "gems" rather than the "wows"? Or vice versa?
Would you prefer warmer weather or are you okay with some chilly springtime temps in the north? If you are open to other destinations instead of the ones you named, you need to describe your interests in more detail. Lisbon is enchanting, but why go if you'd be more fascinated by Athens or Berlin? For nightlife, you might feel more drawn to Barcelona and Antwerp than Venice or Amsterdam.
Europeans themselves argue about which cities of Europe are the most important in Europe! If you look at it one way, Berlin and London are much more important than Venice and Paris -- and yet, for many people, Venice and Paris are at the top of their lists for places to visit in their lifetimes. So pick what makes you feel enthusiastic to see.
As for hotels, Booking.com is a great resource for selecting and booking hotels all over the world.