First the disclaimer.............I grew up on Cape Cod, have eaten clams 25 ways from Sunday, and would probably have my passport revoked the next time I go over the Bourne Bridge for the following, but sometimes even I like it "quick and easy".
In a pinch...and still better than a lot of commercial outfits, I take a can of the store-bought brand (The Red/White Chunky kind, usually) To it, I add a tuna-sized can of Chopped (not minced) clams drained, but saving the juice, a cple of pieces of cooked bacon, andouille sausage or my favorite, hard-to-get, Linguica. I put about a 1/2 tsp of minced garlic, 2 tsp of minced onion and then heat. I add back part of the clam juice to thin it a bit and give a little more flavor.about 1/2 of the drained juice. Server it in a bowl with a pat of softened butter and sprinkle some GOOD paprika on top for color.
Once or twice I gave up my saltwater-in-the-veins badge completely and added some corn....and/or some shredded cheese to the bowl. Nice change of pace, but usually I do not put them in. Over on Chowhound, the purists are raging about a post asking if it is ok to add corn. My feeling is.ok, it may not be "pure" New England Chowder, but if it tastes good.........and I'll bet more than one cook on Cape Cod 100-150 years ago played around a bit with ingredients.
As for Manhattan style........well, sorry, there's still enough of the salt crust on my soul to consider that Tomato Soup with some clams added. Rhode Island (clear) chowder I do like., especially if a few sauteed carrots have been added.
I'll be on the Cape next week so if you folks hear of an earthquake or other "disturbance" in the area, you'll know my friends and family read this and figured out it was me. If they do, I"ll report back on what is like to be "Keelhauled".