The best technique I’ve tried when starting new gardening beds is the lasagna method or the no-dig method. The idea is simple: you put down cardboard or old newspapers, straight on the grass where you want your bed to be. You cover the cardboard with straw, manure and all the compostable materials you can get your hands on: coffee grounds, egg peels, old vegetables… On top of this you can add some more manure and top it off with a fine layer of soil (store bought is great, but I use soil that I find in my garden and that works too). What you want is a good mixture of materials that will trick the earthworms upwards to munch on all the compostable material you added and then turn it into dark and nutritious soil. For extra great result, I try to find manure packed with worms already. They will love their new environment and boost up the decomposing in a few month.