1. Get your cables off the floor. You can buy nice looking ceramic risers or you can make your own out of wood, cardboard, upside down Styrofoam cups, whatever.
2. Get rid of unnecessary connections, espcially on the speakers cables/binding post connections. Banana plugs suck big time and spades are only slightly better. Bare/or tinned wire is best on your speaker wires. Get rid of your binding posts, if you can. Use my binding post bypass system or simply hardwire....you won't believe the difference.
3. Treat all you cables with one of the latest silver contact enhancers. I use the Extreme AV Quicksilver Gold....really makes a big, big difference....you can treat all the ends of your cables, fuses, tube pins, etc.
4. Keep your low level cables away from power cords, or at least cross at right angles if they are near.