Tennessee Jed's
(http://www.barbeque.li/) is an old fashioned family-owned bbq restaurant in wantagh.
Long Island is a lot like New Jersey and parts of Connecticut in as much as a there are a lot of 24 hour diners that serve pretty much anything whenever. Young people congregate in these diners at odd hours, and they can be found spread out on the major roads like Jericho Turnpike or Sunrise Highway. There are also many seafood restaurants especially with local clams and mussels-local Long Island specialty foods. Because there are so many local restauraunts, many Zagat rated, with influence from European families and the nearby international cuisine of New York City, a Long Islander wouldn't recommend to eat at a chain restaurant that could be found anywhere such as Applebee's, the Olive Garden or Red Lobster. They are of course readily available on Long Island, but it is really a shame to not try privatley owned eateries that are equally priced but more distinct than the chain restaurants. Try one of the following:
Jedediah Hawkins House
The restaurant at the Jedediah Hawkins House (http://www.captainhawkins...) in Jamesport is really good and in a beautiful setting.
Peter Luger's Steakhouse
Est. 1887 in brooklyn is one of the best steakhouses in new york (http://www.peterluger.com)
Briemier Pies in Riverhead- people travel from the city to eat one of these delicious pies- you wonder what is in them that makes them so addicting!
The Kitchen, a Bistro, in Saint James- voted the best restaurant on Long Island of 2009. French Mediterranean cuisine using local Long Island ingredients.
The sister eatery, The Kitchen, a Trattoria, offers light, rustic Italian cusine. Also located in Saint James, this is a bit different than New York Style Italian that leaves you feeling like a huge salami about to roll out the door- this is the real deal. Light, delicious non-Americanized Italian food that you would find at a trattoria in Italy.
Many major fast food chains and chain casual dining restaurants have locations on Long Island.
Be sure to visit a local farmstand, especially those out east and on the North Fork. Local produce and farming is a major industry on Long Island.