Most often it is suggested that you plant the acorn on it's side; it will shoot the radical (future tap root) first and - sometime later (can be as late as the following spring/summer (early summer if you planted in the preceding fall) you will see the tree emerge and begin growing. Since both the radical/taproot AND tree come out of the pointed end of the acorn, there is less chance for an orientation problem with the tree if the acorn is on it's side. I imagine you could grow trees from acorns planted with the point down; I just have never tried to do so.