"The only way not to have to write things down is to write them down so you remember them well enough not to have written them down."
Fold up a piece of computer paper in half 3 times (roughly 2"x3") and keep it in your back pocket. Keep a pen in a front pocket or where ever is comfortable and you will never forget an idea, phone number, etc ever again. Go over your list at the end of the day and throw the items on a to-do list (your computer, calendar, etc), the peace of mind that you will get from knowing you have your information than not, will make your life just that much better. If you always have ideas running through your brain like I do, you can fill up the piece paper before it starts to fall apart and it gets pretty interesting to see where your brain has been going... after a while you will notice you remember things without even looking back at the paper just because you wrote them down, hence the Mental Catch-22. This article couldn't prove it more, http://www.lifehack.org/articles/productivity/writing-and-remembering-why-we-remember-what-we-write.html
FYI- Try and transfer the info fairly frequently since you will prob forget the paper in your pants and toss them in the wash, the paper eventually falls apart from being folded so many times or just plain leave it somewhere and can't get it back...
On a unique side note, http://savethetextsavethewords.blogspot.com/, weird but interestingly true.