Where to go is the subject of about eighty percent of my conversations with fishermen. Trying to answer that question is complicated by weather, tides, time of year, etc. There are an incredible number of places on the North Shore that continue to hold big stripers in numbers. Here are several around Gloucester that are easy to reach that over the years have been consistent producers.
There are a set of rocks just outside the mouth of the harbor near the shoreline that are just a natural holding spot for big stripers. On an incoming tide the harbor side of the outcropping is a favorite place for big fish to wait for the bait fish that come swimming on by.
There are two great ways to fish in there. Anchor up as near as you can to the stones and start chumming. Be patient. Use small chum bits and get a good line of scent and food going with the current. Now stop a few minutes. Wait. Now put some good big chunks on your lines and drift them on out the back of the boat. Use different rigs at different depths using bobbers or balloons until you get a response.
The second method uses eels. The big fish here love eels. Again, there are techniques for fishing eels that is a column unto itself, but this method also will produce big fish. The best time to fish here is a night or very early in the morning.
This spot requires good boat handling and charts. On the north side of the cove is a set of rocks that come out from shore that are hidden by high tide. They are dangerous in a heavy surf, but are an incredible spot for stripers. Before fishing there at night you really want to scope the whole cove out during daylight.