I use the tickle file for this. I have a hipster PDA and my system is entirely 3X5 index card based. Any “waiting for” item gets written on a card and tickled for an appropriate time period. When that day arrives I reasses the card (item). I decide what the next action is immediately. It may go into the Hipster as an next action (“call bob about my hammer he borrowed”). It may get tossed if it was previously done. It may get re-tickled if it needs more incubating time, or if the terms have changed a bit.

My tickler is a safe system for me. I dump it every day and I try to make my cards descriptive enough so that things won’t get lost.

And a little bit of my own 2 cents…I think that index cards work better than lists any way. You can deal with each item the card represents on an individual basis. You don’t have to recopy on multiple lists. No confusion as to what list to keep the card in. One card, one item, one physical space (hipster, tickler, “project hipster”) to keep it. So far so good with me.