Not much info given Kivi. Factors to consider may be access, depth of fill, material gradation, water content, desired result, etc..
One method I've used and seen done before is Deep Dynamic Compaction (DDC). This is the simple brute force method of dropping large weights (10 to 30 ton) from a crane in a grid type pattern to cover the site and densify the soils down to 20 or 30-ft. Simple but it works and is not too costly.