At the request of a good friend who's planning to backpack in Europe, I've catalogued some tips and tricks that I used when I trekked through Europe for three months with one carry-on suitcase. It's everything I found useful or would have liked to know, and I hope it makes your trip a little more about the experience and a little less about logistics.
How to pack:
This video shows you, literally, how to pack like a pro. Although I didn't discover this until afterwards, it would have made bulkiness so much easier. Alternatively, vacuum bags are magical.
Before you leave:
Download the metro/bus map apps for all the cities you're going to. There's nothing worse than trying to squint at a faraway map in a foreign language for the next stop on a crowded subway.
Download a currency converter app. Who would have thought your dollar would get you so far (or so little). If you're going through Europe, make sure you know which countries don't take the Euro (UK, Scandinavian countries, Czech Republic, Hungary, etc.)
Scan a copy of your passport and email it to yourself, just in case.
Get a Google Voice number before you leave so you can make/receive calls and texts abroad for free via your laptop or phone. Make sure you do this when you're still in the US since you can only sign up for the service with a US IP address.
I've found skyscanner.net, booking.com, and hostelworld.com to be reliable sources for booking. Anything above a 7.5 rating on booking.com is generally decent. Flights are often cheaper than taking the train, but add in transport time/costs.
Figure out how to get from the airport/train station to your hotel and back for each of your stopping cities. This means knowing the bus/subway number and route stop names for your hotel. You should keep this with you. The rest of the trip can be planned at the hotel, but make sure you do this while you still have internet access, aka before you leave so you're not stuck unable to make international calls or load a map without data.
It’s nice to have a detailed itinerary of where you’re supposed to be in your phone that you can access without WiFi. It keeps everything in order, and you’re never scrambling for the exact time the train leaves. Here's a PDF screenshot that I carried with me:
What to bring:
If you're flying with budget airlines like Ryanair or easyJet, many of them only allow you one carry-on item. One. As in, if you have a suitcase already, you can't bring another backpack larger than a small purse. Solution: Pack a foldable backpack in your suitcase so you can repack necessary day gear without paying for another carry-on.
Look at weight requirements. easyJet doesn't have one but Ryanair is adamant about weight restrictions, and you get slapped with a hefty overweight fee (something like €20 per kg). This was a godsend.
Definitely bring a water bottle so you're not paying tourist fees for water. The Brita water filter bottle is great for most countries (probably not Morocco) for fill-ups throughout the day.
Things to make life easier when you're there:
There’s no need to buy an international data plan. Simply load the Google map of the city before you leave the hotel, and you’ll have a fully functional map as you navigate within the city without WiFi. The GPS location tracker still works, and you’ll never get lost. I usually “star” my hotel on the map so it’s easy to locate.
If you need free WiFi, McDonalds and Burger King are your best bet. They're ubiquitous, (un)fortunately.
If you're doing a short overnight trip and wear contacts, leave the contact solution bottle. Just fill your empty lens case with fresh solution so you can use it night of.
What to do, see, and eat:
Wikitravel will get you through anything. It's a great start to understand the history and customs, figure out how to get from the airport/train station to the city, make a list of which local foods are not to be missed, and know what to watch out for in terms of safety and staying away from sketchy neighborhoods.
Don’t get caught in tourist trap restaurants. Find a few restaurants on TripAdvisor before you venture into the city and “star” them in Google maps. It’s good to have a few pre-researched options for every meal - sometimes restaurants close on random days or are too full for walk-ins, and you'll never be without options.
If you’re on a budget, make lunch the main meal of the day. There are usually good set lunch deals at most restaurants, especially in Prague. Picnics and farmers markets are also great options. If you're venturing into Scandinavia, staying at a hotel with free breakfast is essential.
Via Wikitravel, find out the names of the major grocery stores nearby where you’re staying and pick up the next day's breakfast on the way back from a day out.
If you're flying with Ryanair, sometimes the airports they use can be remote and far from the main city airport (such as Luton, Stansted, Gatwick, versus London Heathrow). Make sure you check the airport code to see if the lower-priced plane ticket is worth the extra hassle and cost of transportation into the city.
Do some Google searches on any sort of day/museum passes for the city. Some are rip-offs (London, excluding the 2 for 1 London Eye deals) while others save you so much time by bypassing lines (Paris Museum Pass). The Amsterdam one is wonderful if you like Rembrandt, Anne Frank, Van Gogh, etc. In general, do some research if you can skip lines by printing off tickets beforehand (Vatican Museum), or if you need to pre-book before showing up (Borghese Gallery). Almost all London museums are free.
Check which days museums are closed! Especially in France, there's one day of the week when museums are not open. The Versailles Château is closed on Mondays, and Centre Pompidou is closed on Tuesdays.
That's all for now. Happy travels!