Ahhh, I remember those days when I was new to being a GM. What fun they were.
The note cards are a great idea, especially for random encounters. Although, when I set up my random encounter tables, I often included more specific notes (i.e. Hit Points and damage for "monsters" and the like). For "planned" encounters (i.e. dungeon delving) I would do a full write-up of the dungeon (cavern, castle, etc.) that included a "visible" description (what the characters saw) a "hidden" description (things like secret and/or concealed doors), any "monsters" encountered and any treasure that might be found. The other thing I would include, or at least bring to the table, was a quick reference sheet with any special notes about skill/stat checks and initiative factors that might play a key role in any possible encounters. Of course, there will always be those "what if" moments when you'll have to look something up, but those can't be helped other than to familiarize yourself with where the "rules" are for those moments in the various guides. It's also helpful to have a quick reference for the characters as well, including spells, special abilities (feats) and the like. There is no way to be 100 percent prepared for any possibility in the gaming session, but every little bit helps, and it sounds like you've already got a couple good ideas in the basket. The best thing I can suggest, in the long run, is to think of those things that were time consuming (at the table) when you were a player, and try to prepare for them.