Method/tactic to extracting information from articles
For your specific example (introductions), I generally need to get through lots and lots of papers to sum up the state of science on a topic, so I read the abstract and the conclusions to make this time-efficient. The abstract should have the main result of the paper with statistical values to back it up, while the conclusions should have statements about the implications of the study and calls for future research. If something doesn't seem right about either, one could investigate the meat of the paper to decide whether to throw it out or save it for reference. Then, I use a program like Endnote and keep notes for how I would cite the paper. This helps me cite while I write.

As a big disclaimer here, there are some papers that might be considered seminal or groundbreaking in a field... these should be read from beginning to end because they represent major advances or shifts in knowledge, approach, etc. That's my take!