my mother has a memory problem

My mother is 87. She has a memory problem and has tried to take meds for this problem, but the side effects stopped her. I live with her and need to run errands from time to time. I have started writing her a big note and taping it to the lamp near where she sits. That way she knows where I am and has my cell phone number to call if she wants to tell me something. I just wonder if there are others that want to share their tips. My mom will ask the same questions over and over. She knows those that are deceased in the family, but those in the community of friends, she can't remember. She will tell me I know I talked to one of my friends just last week and I will say no, you are just remembering years ago when you had a conversation with them. It is really difficult to answer or try to rephrase answers over and over. Please share tips if possible.