Use the Find feature to find all the people who play golf. If you organise functions for your firm, just add to your collegues notes, attended this function, sales forum, seminar. Next time you want to organise one, or find someone who attended, use the find function to find all those people who attended. You may forget to mention these. You can even use it for a strenuous drug regimen, write down the drugs you have to take daily, set a repeating alarm, then cross them out when you have taken them.
Same thing applies to fitness.
The categories in To Do can also be changed, not only can you have sales related To Do's, you can change them to things like Today, Tomorrow, Weekly, Monthly. Or Day, Evening, Weekend. Also you can use them for things like Weddings, Holidays, Projects, Boatbuilding, Fishing, meeting management and sales targets, any thing that needs organising. The date book can be used as a personal journal, writing about day to day events. Especially on holidays and trips, which means that later you can return to it and find the name of that little fishing village, you had lunch in.