If there is a most understated key to success, it would have to be networking. I know, I know... "networking" seems like it is just a buzzword (over-)used by your undergrad institution's career center. And maybe it is.
Or maybe it's not.
During my first two years of undergrad, "networking" meant something business majors did, schmoozing with CEOs while crossing their fingers that the person in the suit pretending to take interest in them would one day prevent their resumé from falling into the reject pile. There was little guidance for how "networking" pertained tomajors.
Somehow, I figured it out on my own, and networking has been a huge part in getting me to grad school at Caltech. Sure, there are other factors like research experience, but when those undergraduate experiences are also (and often just as) competitive, you need a way to set yourself apart from the rest of the application pool.
There are some programs that require you to establish a connection with a mentor pre-application (e.g. Fulbright), but many times making a connection is not a mandatory part of the application process. But don't mistake "not mandatory" for "optional;" to be competitive, making an impression off-paper might help your impression on-paper (or on-line? Either way, I'm talking about your application.).
Fortunately for you (and your bank account), networking doesn't require you to wine and dine your prospective.
One way to network is to let others network for you. Do you like the research your academic advisor does? Great! Ask them to connect you with their advisor from when they were a grad student or post-doc (unless they've totally switched fields, in which case you are out of luck).
Once you are deep enough into your field, few enough people do research similar to yours that it is almost as if you are in an exclusive club with your own reunions (conferences) and holiday dinners (divisional receptions at conferences), and quite often when you hear that someone from your field gotten an award, you swell with pride (or maybe that's just me, too excited to function well in society). Sounds like a family, huh?
So if your interested in pursuing research similar to that of your advisor, look no further than your academic family tree and ask your advisor to hook you up with your academic grandma.
Conferences are a great way to meet people, even if you don't participate in the networking events set up at large divisional meetings. If you're attending a conference, you are (hopefully) attending talks, and lots of them. If someone gives an intriguing talk or is the one person in the room who seems to share your distinct research interests, go up to them during intermission and say hi.
My best experience with this was at theNational Meeting in March 2015. There I met Marco Allodi, a (now-graduated) PhD student doing spectroscopy in the Blake group at Caltech. Not only was he doing spectroscopy, but he was doing the same type of spectroscopy I just received a Fulbright to do in Germany. Furthermore, Geoff Blake, Marco's advisor, is an astrochemist. AND Marco had done a Fulbright in Düsseldorf, north of Köln where I did mine. AND we were both Goldwater scholars. Uncanny, right? Anyway, Marco was an awesome resource during the grad school application process. He even Skyped with me to talk to me about Caltech before I made my final decision, giving me the down-low on things like community, housing, and research. It was awesome having a student's perspective, and his insight was a big part in me choosing to go to Caltech.
Of course, there are lots and lots of people at conferences and sometimes not enough time to connect. To overcome this, I recommend taking a stack of contact (i.e. business) cards with your email and some info about what you do (mine are a condensed CV). That way, if you get the chance to say, "Hi, my name is X, and I am interested in your research," and not much else, you have the card to fall back on.
Another way to network is to go visit a lab that does research in which you are interested. When it comes to grad school, this often takes place during recruitment weekends, where you get to meet prospective advisors and grad students and learn about what is being done in a lab while getting a feel for whether the lab is a good fit.
I didn't actually get to go to any recruitment weekends because (1) I was in Germany and airfare was really expensive, and (2) I was grounded by my doctor because I was in the eighth month of my pregnancy with Günther.
I did, however, the next best thing.
While I was in Marburg, a three-hour train ride from Köln, I emailed Geoff Blake from Caltech to see whether he was accepting students to his group the following year (i.e. right now). Great timing: he was on sabbatical in the Netherlands and was visiting the Laboratory Astrophysics group (which I was joining for my Fulbright) the following week. So, I hopped on a train and met him. Unfortunately, I went to the Universitätstraße stop on theinstead of Universität (amateur's mistake...) and missed his seminar. My twenty-minute walk in the pouring rain wasn't for nothing though; I still got to chat with Geoff about Caltech and his research while getting a feel for whether Caltech would be a good fit. I imagine you'd get the same insights at a researcher's home institution too.
Perhaps the easiest way to network is via email. It is fast, it can be done from anywhere with an internet connection, and you have a written record of what the person said, in case you forget. On the other hand, researchers get a colossal number of emails, so yours might get lost in the slew of newsletters and calendar updates. Moreover, it is a lot easier to ignore an email than a physical person.
When writing an email to a prospective PI, it is important to be professional, brief, and complete. Introduce yourself, mention that you are interested in the recipient's research, and (where applicable) give your relevant background (research experience, coursework, etc.).
I recommend checking out Applying to Grad School - Emailing Professors 101 on the Caffeinated Confidence blog. It provides an excellent overview (with examples!) of the process of writing emails to professors or other researchers. The blog also gives examples of subject lines (e.g. "Prospective Grad Student Inquiry"). You can also use the subject line to sell yourself a bit and separate yourself from other prospective students who took the initiative to send emails. (I used "Goldwater scholar interested in astrochemistry research" and "Prospective chemistry student interested in astrochemistry research" so the recipient knew that I was interested in their research and that I wasn't just sending out a mass email to everyone in the chemistry department.)
An important note on emails: Never send out mass emails, but tailor each email to the recipient. Sure, you can follow the same basic format and keep certain chunks the same, but talk about why you are interested in that specific person. Did you read one of their papers? Did you attend one of their talks? Did you peruse their website? Always address the email something like "Dear Professor Science," not just "Dear Sir/Madame" or "Dear Professor" (which makes it totally obvious you are sending the exact same email to everyone).
If you don't receive a response, don't sweat it. You can try again several weeks later (when the professor has undoubtedly forgotten about your email). If you still receive no response, move on; that person might not be interested and most likely isn't worth your time.
So that's it! Networking is that simple. Intimidating, but simple. And it could make the difference between your application being put to the top of the pile versus the trash can. It might even land you a summer research opportunity without submitting an application. Regardless of where you are in your academic career, networking can be a useful tool in advancing yourself.