Pruning Grape Vines

My property that I recently purchased also has many grape vines that have been neglected for at least 15 years. While the business of renovating a house that was also in neglect has taken priority, as I mentioned in my last post I have finally begun pruning the grape vines, which today, produce few if any berry clusters. The ones that do produce are not that tasty. So, I'm just trying to control overgrowth at the moment and will keep you posted on progress or set backs. If anyone has any thoughts, please let me know. I'm trying not to be too drastic, but certainly assertive in the pruning. Thanks.