Get yourself a day planner, calendar, etc. It doesn't matter what kind. You could use a small 2 year planner, a dollar store planner, or go all out with a name brand day planner. It really doesn't matter. You just need to find one you would actually use.
Now the important point - put everything on this one calendar. Put all your appointments, meetings, kid's appointments, soccer games, practices, school PTA meetings and also your home biz work in the same planner. This way you can look at your planner and know what everyone has to do that specific day or any day in the near future.
Another important detail. Carry it with you! You'll save time because you can give an answer right then and there instead of saying "let me check my schedule".