For Birthdays we go by each month and put all the cards on the wall unit ready to post at the appropriate time. We also write the date on the back so we don't forget.
For people's names it is easy if you think of some characteristic such as 'Smiling Sandra', 'Funny Fred', 'Happy Henry'. and add it to their name.
Groceries we usually take a list, but add to it in the shop :-)
We both have a diary to put important things in as well such as dentist or doctor appointments. OH also does a spread sheet with the names, birthdates, age, tel no, email address and home address on them which is in use all the time.
At Christmas I make a list of what I got for whom and keep it for next year so I do not get the same thing twice.
Getting around we use a satnav.
Also if you are computer literate you can set the reminder on your computer to flash up on important dates.
So far so good! When we forget where we keep the computer then we are in trouble!