I wasn't the person to keep a sort of diary up until a few months ago when I found out how you can use Google Calendar really easily to keep one. Since then I started keeping a business diary and my organization and productivity has soared since.
Why keep a business diary
The reason is pretty straightforward here I think. If you keep a diary (and do it well) you have a searchable database of everything that happens in your business, just like if you would keep a personal one. Since your business is much more than emails and word files you can't just archive those.
What if you want to measure your own performance. If you operate a website you might want to know what day you thought about implementing a new ad feature and what day you actually started and finished.
So far keeping a business diary would have been hard, since you could do it on paper, which is both time consuming and non-searchable, or use text files and so on, which are a bit cumbersome.
How to keep a business diary
The basics here are very easy, how and in what way you wish to elaborate on it is then your own choice. I simply create a calendar named "Diary" and create events in that calendar after the fact. If I am in front of my Laptop and I try out a new web service to review on my blog I would quickly go to Google calendar and create an event named "Tried Web service for post".
When I am away, or many things happen quickly at once I update my calendar at the end of the day. This way I can go back and see key points of every day, or I can even search for specific events.
