Don't waste your time. It's extremely rare for a studio to even open an envelope containing an unsolicited script, and for the big studios - Universal, Fox, Paramount etc. - it'll end up straight in the bin without a second thought.
Read
this. I haven't read the whole thing but it sounds similar to the stuff I've heard elsewhere over the years.
From my perspective, networking is the go. I've built up relationships with other local filmmakers over the years and there's been a cross pollenation of different people working on different projects in different capacities. I'm content to just make stuff I've written on my own (while also working on other's projects) till I have a decent showreel of material - whether it's screenplays, effects work, sound design, whatever - that could be shown to a production or effects house.
