These are some of my favorite strat upgrades.

1) New Pickups, I would suggest the basic Fender Hot Noisless. There's absolutely no hum, and they have a great clean tone and sound awesome with some overdrive or distortion.

2) Tuning Upgrades: New tuning pegs, locking, american standard. Add 2 extra springs to the tremolo, to make a total of 5 springs, helps tuning stability w/ the tremolo. If you want to get fancy, get the gold plated tuners, really doesn't make a difference but there so shiny!