I used to "make a mental note " after uncovering someone's likes or wishes for future gift giving, which then evolved into a notebook filled with names and ideas. That worked great, but now to prevent this info from being discovered by the giftee, I created a running email to myself, always ready for editing by adding, deleting or making changes! It's always at the ready, no matter where I am!
Print out your email and use it as a shopping list at Christmas also!
LOL I do that! My Email program saves drafts in a "Drafts" folder (go figure) and I use the Drafts folder to keep track of various things that I update regularly. It's a good idea!