You never know who your peers will become

In the comments section of my last post about networking at conferences we discussed whether as an early trainee it makes sense to randomly go up to senior scientists just for the sake of networking and this brought up a couple of excellent point which I think merit an independent post. 

1) As a young trainee (grad student, early stage postdoc) you feel that you are not justified in going up to someone without a valid reason, i.e. a brilliant question about their work or wanting a job in their lab. It's scary and daunting and often they are in a huddle talking to their equally famous friends. I tend to go back and forth about the schmoozing just for the sake if it. I have friends who are fantastic at it and will just go up to anyone and engage them in fascinating conversations. This has made them well known to a lot of people and has resulted in a lot of exposure, because the more people know who you are the more they will invite you to speak at symposia and meetings. Unfortunately, science is a popularity contest, in addition to your publications and grants, your tenure also relies on how many national and international talks you have given and on how many meetings you have been invited as a speaker. These early interactions to "make yourself known" can make a difference. While introducing you to people should be your advisor's job, some advisors are not as adept as others and you need to take your networking into your own hands.
This said, there are multiple ways of networking, and I find that small meetings are much more useful than large meetings. I hardly ever meet people I didn't already know at large meetings, but at small meetings you can have a meal or a drink with lots of new people in a much less frantic environment. Getting to know people happens over time. If you genuinely enjoyed a talk, just go up to the speaker and say what struck you. Very very few speakers are 100% sure that their message got across and they will be happy to hear that they made an impact on a young trainee. This may lead to a brief conversation. If the person is in your field, you will see them again. The next time you'll remind them you met at the such and such meeting and talk again and this person will begin to know you. Years later you go on vacation to their country and say "Hey, can I come see your lab?" and they invite you to give a talk and talk to their students. There you meet other faculty who would like to invite you to a symposium they are organizing...and maybe a few years later one of their awesome students becomes your postdoc. True story (potential postdoc still wishful thinking). You never know how a scientific relationship will progress over time. The important thing, I think, is not to expect the world from that initial interaction. The people you need to know, you will see again and again and again, so you can network bit by bit.

2) Never underestimate your friends. The postdocs and students you work with already ARE your scientific community. You all can grow up to be the keynote speakers you admire at the meetings. So when you go to meetings, it is often easier to strike conversations with other students and postdocs. You can share your experiences, learn about their work and their institutions and just start building your network from the bottom up. I can say that right now 70% of my network is people at my level or immediately above I have met through grad school and postdoc. Many have progressed to faculty jobs, they sent me examples of their grants and job applications, they read my stuff, they invite me to speak. Some have been really close friends for almost 20 years, some I have met as conference buddies (people working on similar things whom I always met at the same meetings), some overlapped somewhere and have kept in touch. Many have moved on to industry or other jobs and they are as important as the academic contacts because you can refer students to them when they are thinking about switching jobs, or you can just talk to them about their experience if you need a pharma collaboration or maybe another career altogether.
Your pipeline can go in many different directions as I discussed previously. My network happened organically throughout the years. There was no intent to have all these people in place all over the world in all different aspects of STEM. They are friends, buddies, people I met over time, who have spread out in often unexpected ways. Everyone watching out for everyone else. If in addition to your grad school friends, you comfortably meet 4-5 new interesting people at each meeting you go to, over 15 years of grad school/postdoc your network will grow a LOT. You never know who your peers will become and it's amazing watching everyone evolve.