how do you organize it?
like do you arrange it according to time of day or just write down tasks to accomplish?
Truthfully, I don't write down work related tasks unless things get hairy since I already know what I have to do and there's really no danger of forgetting. Besides, the constant schedule changes of the people I work for makes actual planning an impossibility. Used to write down people's hours but now use another notebook for that. In the planner I write down annoying bullshit that I don't have time for and will be prone to forget, like dentist appts, seeing the bookkeeper, etc, or second-tier personal appts and obligations. Chickenscratch records of things said during a conversation (usually by the other) on a particular day can be handy to reference later if you can read your own writing. Also, it's a good place to store infrequently dialed numbers so I don't have to scroll too far in my phone on a daily basis. Sometimes it's just good to have a notebook handy to write down that you need eggs.
Also find it handy for recording job details, variations, etc, on the day I'll be typing up invoices in order to remind me what to bill. It usually serves as an impromptu file folder in my vehicle too until I get to the paperwork on the weekend.
