Honestly, the 848 is pretty reliable. If you're just tracking for fun, get a copy of the torque settings and go through major things like caliper and axel bolts to make sure they're set to spec. Also a huge "must" is to buy a oil filter nut with safety wire provision and get that thing safety wired to somewhere on the engine. This way, it will be almost impossible for the nut to come loose and some track day providers require the nut to be wired. Some people even safety wire the oil filter, it's a requirement in racing.
A lot of people go over-kill and change their oil before every track event. If your engine is running well, if your oil isn't black every time you change it, then you can probably get away with not doing anything special with the oil changes.
In terms of extra parts... If it's a stock bike, there isn't much to worry about. If you crash, you'll break levers, bend bars and probably damage other things, so your day is over anyway. If it's a specifically built track bike which already has clip-on's, levers and rear sets, bringing replacement parts for those items is nice so you won't ruin a day from a simple lay down. However, be forewarned that some track day agencies won't let you back on after you crash anyway, especially if you caused a full-course red flag. So brining spares is great for dedicated AND BUILT track bikes, but for your average street bike, there usually isn't much you can do.
