How do you prune grapevines ?

Not sure if this is the right forum (or even the right site) but you've never let me down before so here goes. I've got this grapevine in my greenhouse and every year I follow the instructions and prune this, and then that and the outcome is always the same.....b*gg*r*all on the edible front, that's not counting the bits that I've pruned which the rabbit can't get enough of !
Anyway so far the main stem has produced several little shoots, I have selected the 2 which are the most vigorous and pinched the others out. This is were it starts to get confusing for me as books which I have read mention laterals and sub-laterals (Portugeeze to me). Could somebody explain to me please what I've got to do next ? Preferably in simple terms and relatively quickly as these shoots are growing 2 to 3 inches a day at the moment.