I have a few different ways I remind myself of things, depending on how urgent/important they seem to me. If it is something I absolutely want to attend to, I email myself a note so that I will be sure to see it.
If it's something that doesn't seem so urgent, or something I'm not sure I'll ever act on, I use a pencil to write myself a short note on a small Post-It. Then, I stick that on the little window over my driver's license, in my wallet. The constant small shifts that the wallet makes as I walk around will, eventually, smudge the pencil marks to the point that I can't read them.
This takes long enough that, if I pull the wallet out and see one of these illegible notes, I know that whatever was on it wasn't ever important enough for me to worry about it. Then, I throw the sticky note away and go about my business.
So, if you ever give me your number, or some info, and I write it down and stick it in my wallet...Well, let's just say you shouldn't hold your breath waiting to hear from me.