I keep all subsequent (dependent) project actions in Next, regardless of whether they will become Next, Waiting or something else once the preceding tasks have been completed.

To keep them as much out of sight as possible I have them all set with No Context and No Priority. All my true Next and Waiting actions have both of these (My Someday actions have only Priority, but no Context).

This means that when I group my Next actions either by context or by priority or by deadline these subsequent actions will appear at the very bottom where they are easy to ignore (white bar on the left - all others have a priority color).

When I want to review my projects to see if there are any additional subsequent actions that can be turned active (Next, Waiting etc) I either go to the project itself OR I group my Next list by Project. When I select such tasks (for Next or Waiting) I always give them both a context and a priority (usually medium) as part of the "re-processing".

A bit crude, perhaps, but simple, and it works.