Verse 2 describes the preparatory efforts the master took for his vineyard. The fence is a protection from animals or thieves that might steal the fruit or harm it in any way. By clearing the stones the master prepares the ground to be easy for the growing vines. He builds a tower in the vineyard, presumably to allow a watch to be set for the protection of the vineyard, and he builds the winepress in anticipation of the fruits of his labor.
The winepress in particular indicates his expectation of an abundant harvest:
"Such a wine vat consists of two basins or pits carved out of the rocks. The upper pit, where the grapes are trodden out, is shallow and large enough to accommodate the workers. A trench carries the pressed-out juices to a lower, deeper pit, where the wine accumulates until it is stored in clay jars or skin bags. The construction of this type of press is usually undertaken by wealthy landowners or by those who press grapes for many farmers. Thus the fact that the master of the vineyard builds a vat in the middle of his own field indicates that he expects his harvest alone to justify ins construction." (Ludlow, p. 114)
Each of these steps follows not only the care of a good master for the vineyard, but the very steps the Lord has taken to care for Israel. Gods laws are the fence around Israel separating her from other who would do her harm. The Lord has led the to a promised land, preparing the way for them (clearing the stones). He has given them prophets to watch over them (as the guard on the tower) and he awaits the fulfillment of Israel's part of the covenant so that she may enter into his rest.
Both the allegorical vineyard and the nation for which is stands fail to produce according to the effort put in. It is not that there is nothing to show, but that what there is wild, and therefore unfit for the desired end. The wild grapes will not make good wine, and wild Israel has not become what it should have been.