I find a paper journal very convenient - I can write it up in bed at the end of the day, or pick it up at any time if something occurs to me. I'm sure there are online solutions out there (like private blogging tools etc) which some people might find easier to use - though I'd be extremely hesitant (well, I basically wouldn't do it) about putting to an online server (even privately) what goes into my journal. Also, I tend to work visually, which means my journal has spider-diagrams, sketches, different layouts, sidenotes, squiggly lines etc mixed in with the text - very hard to find software that can do that so easily!
just another thing I'd add, for anyone considering starting a journal: I've found that I can sometimes be 'stuck' on a particular line of thought. Then when I write it down, and I see it in black and white, this triggers 'something' that quite often allows me to process it differently, internalise it, frees up whatever blockage or blind spot and allows me to 'move on' to the next thing. It really is a great, useful tool for learning, especially when used in conjunction with all the various reading material here such as the psychology / narcissim stuff. Also it is a great way of looking back and observing how one's state changes, and how different i's manifest over time.
Another useful learning tool, is then publically blogging the understanding that comes from this process, ie: short articles about ponerology or whatever. This is good for organising one's knowledge-base, but is also a way of 'giving back', putting that processed knowledge out there for other people to benefit from.