Why do you need the log?
The standard Franklin method is great if you need a chronological record. Say if you bill for time, or if you need a detailed log for CYA purposes. It's the record you turn to when the Congressional hearing chair or the prosecuting attorney asks you exactly when a particular meeting on a particular topic took place. (Of course, it's also a record that such entities love to subpoena.)
If you're collecting project-specific information, on the other hand, you might want to store it in a project-specific way, such as in the "car information" folder that others have mentioned.
Personally, I use a variety of methods.
For interview notes. notes from conferences, or notes from meetings with clients, I use a bound notebook with pre-numbered pages. The back pages become an index to the volume. These are all situations where I need to capture a large number of items at once, and where I might need to refer back to the notes for several projects over an extended period. These situations, in other words, come the closest to the traditional "diary" application.
For ideas and short notes -- including gems I glean when processing the above notebooks -- I use index cards. They're cheap, portable, and easy to shuffle around, which makes them ideal for transient applications like interim "working notes" for specific projects.
Most data from outside sources -- articles, web pages, emails -- comes to me electronically, so I store it electronically, mostly in a DevonThink database. Electronic storage has the advantage of infinite searchability and replicability, plus it's much more scalable when large amounts of material are involved. I suppose I could scan or transcribe my paper notes to electronic form, but the rewards have never seemed to justify the tedium (to do it myself) or the cost (to hire someone).
Hope this helps.