Dig holes as deep as you can and about 4-5 feet apart. You are just tring to loosen it up. If the soil is humus rich then you can just add some bat guano or something, also you should add a small amount (handful) of hydrated lime in each hole. (don't add too much lime) If the soil is clay then you will need to add some potting soil to the loosened soil. If it is too sandy then you will need to again add some potting soil. Here's how to tell what kind of soil you have: wet it some and then grab a fistful if the fistful remains in a nice loose clump with no sand running through your fingers then you've got good soil. If you grab a fistful and it remains in this clump and is somewhat clay like then you have bad soil and will nedd to add the - soil - guano - lime. This should give you a good healthy grow.

THis is a bit tough to describe but i hope this helps.

Herbus