Basically lock ups, driver restarts inside windows, BSOD, artifacts, rendering errors. Things like that.
You can email Jacob from EVGA and give him your serial number along with details of your issues. You then must register your card on their website, supply a CC# for the cross ship (they don't charge you unless they don't ever receive your card), they ship you a FTW card first via 2 day air and provide a shipping label for your SC card that you use to send your card back.
It was quite painless and when I did it the process went like this.
Sunday I email Jacob, Monday at 4:00PM I had an RMA number, Tuesday my card shipped to me, Thursday I had the new card, friday I shipped my SC card to them, monday they received it.