I find that the thing that needs to be reiterated the most times is how goblins may be played into the army; I think the confusion comes from the fact that you usually first teach the rank 1, which has significantly different placement rules than the other two. Inspired by the play-aid in this Essen booth photo, the attached aid is intended to be placed alongside the army area of a new player (or just someone who wants a refresher) and contains placement rules for new goblins. Two per page, so print two copies for a full set. Cut each strip around the edges, and score at the marks between cards to fold in a "Z" to easily fit in the game box (or even in a card box if you're using one instead of hauling the whole thing around).
v 1.1: Fixes error regarding discard cost for rank-1 goblins.