vaccume leak

i have 2003 crown vic. my mechanic tells me that i have a minor vaccume leak in my car. can some body help how to detect a vaccume leak. i dont know what to do . my car misses a lot while driving. can it happen becoz of oxygen sensors. help plz.

Get a can of carburetor cleaner spray along sides of intake manifold. When the spray hits a leak the engine will smooth out. You can check around vacuum hoses and fittings.