Welcome to the forum
I won't skirt the issue and will directly say it-- NH is not the duck capitol of the flyway. Good duck spots are hard to come by and highly prized. With all the gas I've burned scouting, I could have bought myself a nice duck boat
Google Earth is one of the greatest tools available to us. Start at your house and work around it eventually branching out. Mark potential spots and go check them out and see if there are ducks. Just because there are none when you look, does not mean that none are there early AM/ late in the day or late in the season too.
Swamps, ponds, lakes, streams, rivers-- are all potential spots. Lots of fields for geese as well. Where we lack on duck population we partially make up for in spots and access to the spots compared to some other states.