|Oh, this one is so SIMPLE I'm almost embarassed to post it.
Get a pack of 3x5 cards or other small, stiff paper that won't get crunched up in an overstuffed pattern envelope. When you finish a project, write down any changes you'd like to add or tips for the next time you sew it. For example, I recently made a knit top. The back poufs out a bit, so I noted " swayback alteration / make with CB seam" on a card, and popped it into the envelope.
Previously, I would have altered the tissue pattern right after sewing, and then I wouldn't bother to make it again. Or I relied on memory for the next version, but I'd forget. Or I would promise myself to try on the first model before making a second, and that rascally project was always in the wash when I wanted to cut out a new one. The card saves you from all of this hassle.
This is so simple, but it took me three years of sewing to think of it. Hopefully everyone else already does this, but if it saves anyone else from three years... that's why I posted it! HTH