Where is the fuel filter located on a 1999 nissan sentra gs 1.6 L.?

On these models, its under the hood to the left of the brake fluid resevoir. it has 2 hoses on it which are your fuel lines it is a little canister type thing, make sure you relieve your fuel pressure before you attempt to remove those lines or youll get a face full of gas.

Look under the body below the fuel filler for an object with two hoses going into it. This is the fuel filter.

i hope this helps
matthew