Well anything that will reduce load on that circuit. So right now, probably that whole room is on the circuit (next time it goes out, check and see what outlets still work, if any, and if anything else in the house goes out). So your options then would be, in order of preference:
1. If you have other electronics turned on, you can turn them off and unplug them.
2. Undervolt the cards; if you're mining i'm sure you're familiar with the process.
3. Not use everything. What I mean is, if 4 cards are running, only run 3.
But ultimately, you need to reduce the load on that circuit or it will just keep tripping at best, or burn your house down at worst.