Asking questions while being presented with a paper or a work from a colleague - (Apr/20/2013 )

I am currently a master student studying life and medical science. I am presented with papers, scientific presentations, lab work etc etc everyday. What I have noticed for myself is that i dont understand the work but I cannot ask questions which will lead me to understand the topic. It seems that the load of informations that I am presented just makes my brain go blank.
How can I improve to ask questions which will lead me to ask questions that will enlighten me with the things that I don't understand???

Help from the community will be appreciated...

I'd say it's a matter of training...look how others ask questions. Also to have sufficient background knowledge is helpful as you can see then discrepancies or relations to other studies and develop a questions out of this. If it's possible you can inform yourself what the others will report (e.g. in some departments abstracts are send to the colleagues) and then prepare yourself about this, try to understand it and try to find stuff for questions.
And finally if you're a beginner or it's not your field of work usually also "stupid" questions are allowed as there are no stupid questions. But this depends on the environment there of course (i.e. if all try to appear as know-it-alls and someone showing that s/he has a gap is considered as weakness and stupidity, then of course not).