People with ADHD have a less than stellar working memory. We are currently working through a workbook by Dr. Ari Tuckman called Understand Your Brain, Get More Done, and the working memory portion has given us a lot of helpful tips and strategies.
His 3 main principles to strategize working memory are (I'm paraphrasing):
These are great strategies. If you are interested in his workbook, you can google it or see it here.