I took this from another site
Detonation can be prevented by:
The use of a fuel with higher octane rating
The addition of octane-increasing "lead", methylcyclopentadienyl manganese tricarbonyl (MMT), isooctane, or other antiknock agents.
Increasing the amount of fuel injected/inducted (resulting in lower Air to Fuel Ratio)
Reduction of cylinder pressure by increasing the engine revolutions (lower gear), decreasing the manifold pressure (throttle opening) or reducing the load on the engine, or any combination.
Reduction of charge (in-cylinder) temperatures (such as through cooling, water injection or compression ratio reduction).
Retardation of spark plug ignition.
Improved combustion chamber design that concentrates mixture near the spark plug and generates high turbulence to promote fast even burning.
Use of a spark plug of colder heat range in cases where the spark plug insulator has become a source of pre-ignition leading to detonation.