Remembering my battleplan! With every encounter I have a generalized plan creatures will take. Most creatures only need a vague plan, usually involving when to flee, but some need more. Leadership creatures usually need a 2-3 round layout. Casters potentially require up to 5 rounds, depending on how powerful they are. The problem is that occasionally I'll forget something in the heat of battle that skews it for the players, sometimes drastically so (forgetting about Counterspell can end an encounter).