In the tool I use for keeping my context lists and projects, Omnifocus, I just put it next after the real next action, set the project to sequential and leave it. Then as soon as I am done with the first one the second becomes available with no more intervention from me. I go ahead and give it the appropriate context right then. No sense wasting any valuable thinking time by re-doing something you've already thought out.

More generally that is what is called Project Support in the GTD system. YOu can just put it with other project support materials.