I find it really important to double enter waiting fors, that is put same item in adgenda and w/f with a symbol to indicate it is in both. Or, put them on same list if the list isn't too long.
I know it is not efficient but this is what happens.
I meet with, call or write to someome and go through my adgenda items. If I am w/f for something from them, and don't have the item tagged to their name in @djenda, I have no cue to remind me to follow up. So, they think I don't care. Or, I have re-contact them when I review w/f.
Also, it may pop into my head, while I am talking to someone, that I might ask them to do something. I don't want to ask them, if I have already done so and forgot that I was waiting for them to get back to me or whatever.