I try to stay focused by creating a personal syllabus for each subject I'm interested in. I add books to them, as well as objectives and questions I'd like to answer. Of particular value has been the habit of setting written products as my objectives. These help me focus on important aspects of a subject as well as help weed out irrelevant reading material.

I use a simple sequential filing system for articles. I assign incoming articles a serial number. I have a file that allows me to browse these by subject and author, but the serial number makes them easy to reference when I want them.