My Google calendar is my very best friend. I put EVERYTHING in there, my kids’ school and extracurricular activities, mine and my kids’ appointments, my work schedule, etc. I share it with my husband. (Still have yet to get him to write down the days when he is away, etc, but we’ll get there)
I used to take the appointment cards from the different places, and put them in my purse or pocket. And they would stay there because I would forget to put them in my calendar by the time I got home. Or I would get the dates mixed up and write them down wrong. So now, I just bring out my phone while booking the appointment, and put it in right then and there, then confirm the date and time. I haven’t missed an appointment since I started this about 4 months ago.