Jim,
There are tons of places to search out on Long Island.
Forge Pond and Upper Mill in Riverhead. Both have easy access and offer super action on bass and pickerel. Live bait - shiners - Fishermans Deli in Riverhead carry's them, plus spinnerbaits, topwaters and jigs work well.
Lake Ronkonkoma is a tough lake as it is so expanse and deep. Always use caution there as winds can kick the lake up pretty good. Try throwing jigs if the water level is up and the trees are submerged. If not a Senko worked slowly on the east side is best.
Another super lake, which has boats to rent is Blydenburg, located in Smithtown. The lake is probably one of your best bets for outsized largemouths. I have not fished this in a while, but I get reports every year of 4 to 6 pound class fish.
As for Laurel, that is another good one. Weeds in the back corner hold large pickerel, while the deeper holes will see good trout action in the fall and spring.
Hope this gets you started, and feel free to contact me at sudsurfer@gmail.com any time for tips or advice
Sincerely,
Tom Melton/Senior Field Editor
The Fisherman Magazine