Allan, Duxbury beach is excellent. It's also probably one of the more under fished spots around when it comes to bass. The area around the powder Point Bridge is a consistent producer. My best advise is to spend time learning areas around there. Read the water, look for rock piles, flats that are near drop offs, etc.
You may want to visit Henry Weston Outfitters in Pembroke and spend some time talking with Jim McKay. Ask him to pull out a chart and give you a few pointers. He's willing to help and he's got a wealth of information about that area. In my Metropolitan Boston Fishwire report last week he mentioned big bass on Captains Flats. I haven't been out there this year, but you can bet I'll be taking the boat down there in the next week or two.
Do you have a 4x4 with a Duxbury beach permit? I'd love to get out and do some scouting by beach buggy.