Traveling within Europe.

Can you provide some more details? How old are you? Which countries do you plan to visit?

In general, 3rd party rail passes (like those sold by ticket agencies like Eurail) almost never make economic sense for adults, sometimes they may for those who qualify for youth rates. Every national rail carrier has their own rates and regulations, so without knowing a little more, we can't delve into specifics.

Trains almost never fill up.

Perhaps not what you are asking or the advice you want to hear.

'34 days and 9 different countries.'
Does this include flight arrival and departure days, if so subtract two days. Subtract at least eight travel movements from door to door in unfamiliar surroundings of half a day to a day each. You did not have time with your original thoughts, does this now give you time to see any whole country? You have barely time to see the many sites of one major city in one country let alone a country.
Essentially - less is more.

'the amount of connecting trains and busses is daunting' - your fault in wanting to do far too much in an almost laughably short amount of time.

'if getting a Eurail pass is worth it '- read this, starting at the bold print - http://www.seat61.com/Railpass-and-Eurail-pass-guide.htm#Should - but maybe you are young enough to make whatever pass pay.

'Do we just approach a train station, show/swipe the pass then enter our selected train?' - Why have you not read the terms and conditions of use?

'do we have to worry about trains filling up before we get there?' - Without knowing where you go, probably not. Although, maybe you are wanting to travel when there is a national festivity or holiday when it feels like half the country (Spain for sure) is on the move, so when you wish to travel will matter.

Niko, just for comparison, I too am going--in the fall--for 34 actual days on the ground and I'm going to only 3 countries. One I have lived in, one I've been to too many times to count and one I've only been to as a child. The first thing you need to to is figure out which city you're flying into and which you're flying out of; this is called multi-city or an open-jaw flight which will save time and money from having to return to your arrival city. Then go to the Deutsch Bahn site to figure out what trains you want to take; the German rail site is excellent for determining arrival, departure, how many connections but not the price if you're not traveling in Germany. For that you'll need to go to each countries' rail site. In many cases if you buy early--such as 90 days in advance for some--the tickets will be cheaper than buying a rail pass and also the seat reservations which are often required. All this planning takes time but is well worth it in the savings.

"Do we just approach a train station, show/swipe the pass then enter our selected train?"

There is no check in area at train stations in Europe; only the train conductor will ask for your tickets once you are on the train and it has left the station. If you don't have a ticket, you get fined and kicked off. In other words, there is no where to show or swipe your pass at the train station.

"Also, do we have to worry about trains filling up before we get there?"

No, as mentioned above, no one at the station is tracking how many people get on a train. If there aren't seats, you just have to stand.

Finally, a word of advice, don't use RailEurope for any information related to fares and schedules. Use the website of the national rail carrier of the country where your journey originates for the best information.

Lastly - rail passes are a waste of money in just about every circumstance. If you share your proposed itinerary, it would be easier to help you make your decision between a pass and point to point.

Other basic tools: www.skyscanner.com for budget airlines, www.bahn.com for help with train schedules.
Nine countries in just over a month is absurd unless you are checking off a list that you will "see" mostly from train or transit windows.
There are no quick answers to your train questions because you haven't worked out what you want to do. This forum and others are full of the same questions, particularly concerning passes, and the accumulated wisdom is that Eurail passes should be the last thing you consider, not the first. Begin by charting a more reasonable route, then look up the various national train systems to find point-to-point prices, remembering that inter-city trains may be much cheaper if bought three months in advance. With the pass you will still be required to make (and pay for) seat reservations on some trips. Point-to-point include those reservations. Some trains get full in advance, the same as everywhere else in the world.
Train operators may require that individual paper tickets be punched by a machine on the train platform; these are for undated tickets. Research the fine print on the vendors' websites. Best advice has already been given: Study the wide-ranging knowledge on Seat 61.

We did 10 cities in 9 countries in 30 days and did not feel like we only "saw them from the window of a train". Not everyone wants to do in in-depth study of place - we go the first time usually to see if we want to return - I would certainly be disappointed if I had booked a week in a city and figured out in two days time that I was ready to leave! While this type of travel is not for everyone we enjoy it. Most travel days we had arrived in our new destination and checked in to our hotel by 1 or 2 pm and had the rest of the afternoon & evening to start exploring our new city. As you have undoubtedly read on this site a rail pass is generally not the cheapest way to go but it is the most flexible. If you will be making hotel reservations in each of your destinations before you leave for your trip then advance tickets should save you some money.
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It is difficult to give very specific advice without knowing your exact destinations - some places are far easier to get to on the train than others - if you plan on Croatia for example going by train can take some time as their rail lines are limited. On the other hand if you are Germany, Austria, Italy intensive then the rail is pretty easy & quick.
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Whether you use a pass

Sounds like you are young and energetic... I have done as many countries in half the days... first trip and we loved it! I have since returned, but my daughter has not...life took over. We were so happy to have seen all that we did and I also did not feel as though
we just 'passed through' the whole trip. Also, what countries are you talking about? Are they easy to get to and close together?
We did our first trip by car so were able to travel on our own schedule. You can see a lot and do a lot in a few days if you make the best of your time... as well as find those places you want to return to. Buying those cheap advance train tickets puts you on a strict schedule... your choice... spontaneous travel and possibly pay more or strict schedule that you may not like in the end.

Nico,

to get the information you need please answer the questions above. They are in order to help you not to be difficult.

If this isn't a two way conversation there is no way to answer your concerns accurately.

Hey Everyone! Sorry for not replying (University demands all my time), but I'm super glad that so many people commented! I'll give a more information of what we are planning, though we are quite flexible with what we want to do, so alternative options are welcome!
I am 19 and my brother is 23, both of us from Canada. This is our first big trip without our parents, and planning it ourselves. We leave April 27th to Barcelona, from where we have a friend (also 23) landing in Marseille on May 2nd. From there, the only for sure thing booked is that we leave Paris back to Canada on May 30th.

Our itinerary goes as follows: Barcelona to Marseille, to Rome, to Venice, to Vienna, to Prague, to Berlin, to Amsterdam, then to Paris. At about 4 days in each city, with 9 cities (But only 7 countries, sorry for the mistake), that would give us a total of 36 days, so some cities will get less or more days, depending on what we plan. We haven't booked exact times to get to the cities yet, we only know what we want to do. That's why we thought to ask people who have traveled around before on what you guys might think would be do-able!
We have considered the option of dropping cities and countries to visit, but likely this will be the only big trip we go on in the next couple years. In addition, all of us are short on money (Again, university students) so were looking for the cheapest travel. We are using couch surfing between each city too!

Here's a couple general points about rail travel along your proposed routes, with the huge caveat that you may qualify for youth or student discounts that don't apply to the overwhelming majority of posters on this website.

For Prague to Berlin on the fastest direct train is €67, but if you buy in advanced, you can ride for as little as €39. Berlin to Amsterdam would run you from €116-149 at full cost, €59-99 in advanced. For a youth ticket on the high-speed Thalys train between Amsterdam and Paris, it would run you €90 at full price, or €50 in advanced. It may be slightly cheaper to take the much slower series of trains through the Netherlands, Belgium and France to reach Paris, but you would chew up an entire day doing this, whereas Thalys takes a little over 3 hours.

There are long distance coach lines in Europe that connect various cities, but I don't know to much about them, or if prices are competitive to rail.

Compare these prices to the daily cost of Eurail pass to see if the the pass makes sense. As noted, for adults, it usually doesn't in terms of cost, for younger passengers, it might.

Vienna to Prague - 19 Euro purchased in advance from oebb.at