As for the log, keep it simple and do what's best for you. If you are a computer geek, or keep other records on your computer, then perhaps a computer log such as a simple excel spreadsheet is the way to go. Or if you have PDA you could keep track of it there. I like bikejournal.com personally.
If you are not a computer person, then perhaps a notebook would be better. Think of it like a ride journal more than a log.
Or if you don't like the notebook, maybe a wall calendar. Wall calendars don't get lost like notebooks can.
