Senex

To answer your question directly, you sift each of the ingredients of your soil seperately, then you mix them together. You sift them seperately because you cannot mix the proportions otherwise. It is like baking. Measure flour, measure salt, mix together. You should get a good book, like John Naka's, and consult the soil charts with respect to the type of tree you have. Different trees require different soils for best results.