Anna
The Best Way to Use your Cell Phone in Europe
Having a working cell phone while traveling in a foreign country is a huge convenience and reassurance, especially if you're going to somewhere you haven't been before and may not be able to speak the language. There are definitely several options for doing this, and the cost and value of each option depends on how long you will be abroad, and how many places you'll be visiting.

Most of the time, I and most people I've talked to, just go with their phone provider's international data plan. You get to keep your phone number and you only pay on the days you need to use data, but depending on your phone company and the packages the offer, this can get pretty pricey. For example, my phone provider will give me 1 GB of data a day for $10 (what they don't tell you is that your data gets pretty throttled after half of that, and you have to pay for each country you visit. This means you pay $20 for one day if you do a day trip over and back to another country).
Going into this trip I was just planning on using my data as sparingly as I could, and trying to go a few days without it so I wouldn't spend almost $200 on data that wouldn't even be very helpful... BUT THEN I found out about a much better option, and I've been sending texts and hanging out on social media quite happily since then!!
As it turns out, a much more affordable option for a working cell phone with all the data you need is buying a SIM card! Here's a brief look at what you need to know...

Before you go:
Before you go, make sure that you phone is "unlocked," meaning that your personal cell phone provider didn't lock your phone, preventing it from working with another SIM card. You also need to insure that you have your passport, as they scan it with the SIM card when you purchase it.
Getting your SIM card:
Go to a cell provider upon arriving at your destination and purchase a SIM card from that company. (I would recommend Orange as they are rated as having some of the best options for foreigners looking for SIM cards). They will even help you put it in if you don't know how so that you can make sure it works before you leave the store.

Different Options:
Purchasing a SIM card like this is kinda like buying a cell phone plan; there are different options for the amount of time it works, the number of texts, and the amount of data. For example, the card I got is good for 2 weeks, has 20 GB of data, allows 1000 texts (iMessages don't count) and 120 minutes of phone calls. The store I bought it from charged me 40 Euros, although the prices may vary depending on where you get it. There is also a smaller option of 3 GBs, 200 texts, and 30 minutes of calling if you don't want to pay as much.
Pros:
For me, the pros are huge. I feel much better about being able to reliably navigate or call an Uber whenever I need to, and at a much lower cost. I like to run when I travel, and knowing I have enough data to look things up on Google maps when I'm running alone is definitely reassuring. This method also avoids the concern that your data is getting throttled. When a cell tower is too busy, people using phones that aren't provided by that company are the first to get kicked off of the signal.
Cons:
In my opinion the cons here are more of an inconvenience. You will get a new number with the SIM card, so you need to give the new number to anyone who may need to contact you because you won't get anything from your old number until you switch the SIM cards back. This could be more serious if you're expecting an important work or personal call, or (as I found out) if you have anything that requires 2 factor authentication to log in, and your phone is the only option.
Below are the front and back of the card that comes in the SIM card packet. The card allows you to punch out a regular, micro, or nano sized chip depending on what your phone needs. An easy way to keep track of your old SIM card is to tape it to the larger plastic card, as seen in the picture on the right.
Overall, I have considered this a massive win and will definitely be doing this every time we travel to Europe. I am on day 3 of the experience, and so far so good. I will continue to pay attention to the experience and if anything changes I will certainly come back and take note of it! Hope you find this information as helpful as I did!
~Happy travels~