Lived there for 10 1/2 years while I was stationed Active Duty at the Base. As you start to go out of town going towards the ferry There's a statue of Samuel D' Champlain and you can park at the top of the hill and walk down to the water. Now you can catch lot's of different fish there, it's at the mouth of the lake where the river flows into it.
Jigs, live bait lures try it all!!! And if you want to try at a big smallie try a chartruese pepper tube jig with a 1/8 or 1/4 oz head. Used to be a killer.
Now if you head out of town the other way towards Ausable Chasm you'll come up by Ausable State park, just drive in and you'll go over a bridge and you can fish down at the side of it, anything that swims in the lake is in the river. If you head further down the road just before the gate you can park and fish either side of the road, lake side or marsh side. Used to be really good fishing on both sides.
Just try everything. I've been to Plattsburgh a few times as they have a Gander Mountain Store and some of my old places are now posted so I gave you the two I know aren't. You can also check with the local shops.
Enjoy
Fatman