I cannot emphasize how much prepping for your action in a combat round makes me like you. I am deathly serious. Even if your idea doesn't work, it at least shows you're engaged and trying to do things. This goes double if you're playing a complex class or role, like a spellcaster in D&D/PF. For the love of Gygax and Arneson, if you play those, you should at least have quick-reference info for your spells and know what they do. I've played with a couple players who literally had to open the rulebook every time they cast a spell, and it wasn't for some weird exception or edge case.