As for planning, I am on the extreme side of the balance. I plan everything out down to probable NPC responses. I'll let some of the others answer any planning questions unless you are like me.
As for tools, make sure you have enough dice. One d6 is usually not enough so grab a handful of them. It is kinda sad to listen to the DM roll the same die 5 or 6 times because he has only one and needs 4. Other resources I suggest are Initiative cards listing initiative, AC, and key skill modifiers for each player. I use these to create the initiative during combat, track AC so I can just roll instead of asking each time. I keep skill modifiers like listen, hide, and such so that I can roll for the players behind my screen without alerting them to anything about to happen. Often times, especially with experienced players, you can skew their actions by saying things like, "Okay everyone roll Spot now."
I would also keep all books needed on hand or copies of the relative sections for reference. I make my players responsible for bringing printouts or the books for any non-core material they are using in their characters.
Since I plan out every minute detail I know all the stats for my cities but if you don't then you will probably need the random generator tables from the DMG in order for you PC's to purchase goods. I would never let my players just buy anything they want because realistically not every town/city is going to have the same merchandise for sale or services for purchase. Letting them buy whatever they want in every town will often come back to bite you.
I imagine you have some mats and token or miniatures already so I won't go into that but make sure you draw out the dungeons ahead of time and kno w your traps. A dungeon is a potentially hazardous place and you really don't want to "wing it" right into a player death.
I'm sure everyone else can fill in anything I might have missed.