Add knee pads and gloves if you're doing serious penetration. Don't touch anything unnecessarily, and never touch anything above you. If you have to swim against current, save energy by pulling yourself along the wreck, but only if you're wearing gloves. Wrecks can often experience current on one side while being calm on the other. If this is the case, stay on the quiet side.
Some wreck divers use pony bottles, while others rig up dual tanks and regulators.
Stay neutral, fine-tune your buoyancy and don't flutter kick inside a wreck. If you do experience a silt-out, stay calm. Hang motionless for a minute or two and the silt will settle enough for you to find your way out.