I put appointments in my mobile phone too with a reminder the day before as well. If not then I just totally forget them. Mind you I turned up for my psych appointment 1 month early because I put the wrong date in my phone. Doh.
I also use have a white board on the living room wall to write down important to do's. This is great and works really well for me.
At work if I have to be in earlier than usual I will write it in the work diary for a reminder for the day before. If it's a Monday I will put it in the Friday before. I also use the work diary for appointments if I have to leave work early as a reminder.
Any messages for colleagues that I have to tell them on certain day like when they get back from holidays I put in the diary as I just won't remember otherwise.
I have my planner now opened beside the computer and phone with all of the appointment dates written inside of it- Marked! NOW- if I miss any of those appointments- I will have be in trouble- but like one of you mentioned. We are just human, and that is what normal people do too; also make mistakes with themselves and miss appointments as well. My DH misses meetings all of the time, and he does not have ADHD (that we are aware of).
Yesterday I took my planner with me when I went shopping and marked off all of the things I had to do in it while I was running the errands. I had a lot to do and if I didn't do that- I would have forgotten everything that needed to get done.
I just got the bill for my kids missed dental appointment- and WAS written on the calendar! 
I just remind myself that even people without ADHD miss appointments occasionally. And that's the goal right- to function a a "normal" level?
I miss appointments when medicated. In fact, of all the ADD traits that provide "spice" and challenge to my day (as well as torment if I let them) time management and keeping track of appointments is still the hardest for me to make substantial headway with. Medicated or not... ADD or not... the consequences for a missed appointment are the same...arrghh!!
my cell phone has been a life saver for appointments. The minute I get the card from the doctor or dentist I put it in my cell phone with a loud reminder the day before. Thank Goodness some doctors offices still make courtesy calls which also helps. I also write it on my office calendar so between the 3 places I am less likely to miss the appointment. It was hard enough when it was just my appointments now that I have 3 kids it is really difficult. I cannot miss my middle daughter's appointments because she has ADHD and the doctor is there on site once a month.
Do any of you still forget appointments while taking the meds? I thought I would stop doing this, however, I mistakingly missed my sons pdoc appointment yesterday. argh! I failed to write it down in my planner. I feel so stupid.
It is a simple mistake, and luckily the doctors office was very understanding though it takes about 3 months to reschedule for another appointment the receptionist- knows how difficult our son can be, and put our son ahead 3 weeks in advance. She is such a blessing!
I have yet to tell the pdoc, who is a child's pdoc specialist, that I have ADHD- was dx'd since his last appointment. I will have our son do the honors because he thinks it is such a huge ordeal that we have 'something in common' and take the same medication. He is eight.
Thanks for listening. I hope that others can relate. This just makes me cringe when I know that things like this still happen. I just want to be able to not have this happen. I try so hard to be organized and to stay on top of things. I feel so much more organized than I ever have been in my life for once. And, my house is that way for a change- until my munchkins get home and destroy it; every day! LOL Then I have to reclean it all over again!
Have a super day!
Julie