I tried paper and log books for a long time (I've got half a filing cabinets worth), but no matter what system I used I couldn't always find what I wanted. (When did I last modify routine xyz, and why?).
Moving to flat ascii files meant it's searchable and has longevity as it doesn't need any specific tool or app. I can also carry the lot around with me - very useful on site.
Well, I never used my log books as an information retrieval system; the prime purpose was to help me remember what I did an hour ago, a day ago, a week ago.
Of course, I have a digital file of timestamped and commented code snippets and pieces of config. But that's just about the activity of coding; I now think a handwritten log is a good idea for anyone, whatever their trade.
The reason I recommend a hardback notebook, is because it offers the best CYA protection (I was caned as a child). It's sorta symbolic - hard evidence, if you like.
[Edit] You can also scribble in your notebook in meetings, while glancing furtively over your spectacle rims, to intimidate the speaker. Hard copy is power.
I use a heirarchy of folders and within them I create a text file for each main task:
\work\customername\StockSystem
MyCust001 - Interface not updating PickStatus.txt
MyCust002 - Add Stock Check Flag to ScanPullStock.txt
MyCust003 - Look at enhancing Batch Split screen.txt
I use the numbers as a quick reference within all my documents.
\personal\Diving
Diving book recommendations.txt
Diving gas tables.txt
\personal\DIY
Standard screw sizes.txt
Choosing new security lights.txt
Getting new consumer unit fitted.txt
I add the date and time to a line whenever I start, or after a break. (Pressing F7 on UltraEdit does this automatically). I can use this retrospectively to see how long things took.
Moving to flat ascii files meant it's searchable and has longevity as it doesn't need any specific tool or app. I can also carry the lot around with me - very useful on site.
Cheers.