All good points, but there are a couple mistakes I often see people (not just beginners) make that did not get mentioned: 1. State the problem (and convince th

All good points, but there are a couple mistakes I often see people (not just beginners) make that did not get mentioned: 1. State the problem (and convince the audience it matters) before rushing to present a solution. 2. Know the background of your audience, and figure out how well they need to know the background to get something out of your talk. And to the grad students: sometimes, when one only has 10-15 minutes to give a talk, it is hard to give one that makes sense to junior members of the audience and still speak to the experts. Don't give up! and don't be shy about asking speakers questions afterwards. Sure, there are some people who think they are too important to talk to grad students (or even faculty) they don't know. The worst you get from asking such people a questions is you get brushed off (don't worry, they're not likely to remember who you are, and it's not likely to have a negative impact on your career). But more often people are happy to go into details, and/or put you in touch with the postdoc / grad student who knows all the gory details, etc. etc.